sql made simple

8/12/2019 SQL Made Simple

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Guide

Introduction to SQL

SQL is a standard language for accessing and manipulating databases.

What is SQL?

SQL stands for Structured Query Language

SQL lets you access and manipulate databases

SQL is an ANSI (American National Standards Institute) standard

What Can SQL do?

SQL can execute queries against a database

SQL can retriee data from a database

SQL can insert records in a database

SQL can update records in a database

SQL can delete records from a database

SQL can create ne! databases

SQL can create ne! tables in a database

SQL can create stored procedures in a database

SQL can create ie!s in a database

SQL can set permissions on tables" procedures" and ie!s

SQL is a Standard - BUT....

Alt#oug# SQL is an ANSI (American National Standards Institute) standard" t#ere are manydifferent ersions of t#e SQL language.

$o!eer" to be compliant !it# t#e ANSI standard" t#ey all support at least t#e ma%or commands

(suc# as S&L&'" *+A&" +&L&&" INS&," -$&,&) in a similar manner.


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Note:ost of t#e SQL database programs also #ae t#eir o!n proprietary extensions in addition

to t#e SQL standard/

Using SQL in Your Web Site

o build a !eb site t#at s#o!s some data from a database" you !ill need t#e follo!ing0

An ,+1S database program (i.e. S Access" SQL Serer" ySQL)

A serer2side scripting language" li3e *$* or AS*

SQL

$L 4 'SS

RDBMS

,+1S stands for ,elational +atabase anagement System.

,+1S is t#e basis for SQL" and for all modern database systems li3e S SQL Serer" I1+15" 6racle" ySQL" and icrosoft Access.

#e data in ,+1S is stored in database ob%ects called tables.

A table is a collections of related data entries and it consists of columns and ro!s.

Database Tabes

A database most often contains one or more tables. &ac# table is identified by a name (e.g.7'ustomers7 or 76rders7). ables contain records (ro!s) !it# data.

1elo! is an example of a table called 7*ersons70

!"#d LastNa$e %irstNa$e &ddress Cit'

8 $ansen 6la imotein 89 Sandnes

5 Sendson oe 1orgn 5: Sandnes

: *ettersen ;ari Storgt 59 Staanger

#e table aboe contains t#ree records (one for eac# person) and fie columns (*


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SQL State$ents

ost of t#e actions you need to perform on a database are done !it# SQL statements.

#e follo!ing SQL statement !ill select all t#e records in t#e 7*ersons7 table0

S&L&' > =,6 *ersons

In t#is tutorial !e !ill teac# you all about t#e different SQL statements.

(ee) in Mind That...

SQL is not case sensitie

Se$i*oon a+ter SQL State$ents?

Some database systems require a semicolon at t#e end of eac# SQL statement.

Semicolon is t#e standard !ay to separate eac# SQL statement in database systems t#at allo!more t#an one SQL statement to be executed in t#e same call to t#e serer.

-e are using S Access and SQL Serer 5999 and !e do not #ae to put a semicolon after eac#

SQL statement" but some database programs force you to use it.

SQL DML and DDL

SQL can be diided into t!o parts0 #e +ata anipulation Language (+L) and t#e +ata+efinition Language (++L).

#e query and update commands form t#e +L part of SQL0

S,L,CT2 extracts data from a database

U!D&T,2 updates data in a database

D,L,T,2 deletes data from a database

#NS,RT #NT2 inserts ne! data into a database

#e ++L part of SQL permits database tables to be created or deleted. It also define indexes(3eys)" specify lin3s bet!een tables" and impose constraints bet!een tables. #e most important

++L statements in SQL are0


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CR,&T, D&T&B&S,2 creates a ne! database

&LT,R D&T&B&S,2 modifies a database

CR,&T, T&BL,2 creates a ne! table

&LT,R T&BL,2 modifies a table

DR! T&BL,2 deletes a table

CR,&T, #ND,2 creates an index (searc# 3ey)

DR! #ND,2 deletes an index

SQL SELECT Statement

#is c#apter !ill explain t#e S&L&' and t#e S&L&' > statements.

The SQL S,L,CT State$ent

#e S&L&' statement is used to select data from a database.

#e result is stored in a result table" called t#e result2set.

SQL SELECT Syntax

SELECT column_name(s)FROM table_name

and

SELECT * FROM table_name

Note:SQL is not case sensitie. S&L&' is t#e same as select.

&n SQL S,L,CT ,/a$)e

#e 7*ersons7 table0

P_Id LastName FirstName Address City

1 Hansen Ola Timoteivn 10 Sandnes


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Svendson Tove !o"#vn $ Sandnes

$ %ette"sen &a"i Sto"#t 0 Stavan#e"

No! !e !ant to select t#e content of t#e columns named 7LastName7 and 7=irstName7 from t#e

table aboe.

-e use t#e follo!ing S&L&' statement0

SELECT Last'ameFi"st'ame FROM %e"sons

#e result2set !ill loo3 li3e t#is0

LastName FirstName

Hansen Ola

Svendson Tove

%ette"sen &a"i

S,L,CT 0 ,/a$)e

No! !e !ant to select all t#e columns from t#e 7*ersons7 table.


SELECT * FROM %e"sons

Ti):#e asteris3 (>) is a quic3 !ay of selecting all columns/





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SQL SELECT DISTINCT Statement

#is c#apter !ill explain t#e S&L&' +ISIN' statement.

The SQL S,L,CT D#ST#NCT State$ent

In a table" some of t#e columns may contain duplicate alues. #is is not a problem" #o!eer"

sometimes you !ill !ant to list only t#e different (distinct) alues in a table.

#e +ISIN' 3ey!ord can be used to return only distinct (different) alues.

SQL SELECT DISTINCT Syntax

SELECT ST'CT column_name(s)

FROM table_name

S,L,CT D#ST#NCT ,/a$)e

#e 7*ersons7 table0





No! !e !ant to select only t#e distinct alues from t#e column named 7'ity7 from t#e table

aboe.


SELECT ST'CT Cit+ FROM %e"sons


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City

Sandnes

Stavan#e"

SQL WHERE Clause

#e -$&,& clause is used to filter records.

The W1,R, Cause

#e -$&,& clause is used to extract only t#ose records t#at fulfill a specified criterion.

SQL WHERE Syntax

SELECT column_name(s)

FROM table_name,HERE column_name o-e"ato" value

W1,R, Cause ,/a$)e

#e 7*ersons7 table0






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No! !e !ant to select only t#e persons liing in t#e city 7Sandnes7 from t#e table aboe.



,HERE Cit+./Sandnes/





Quotes &round Te/t %ieds

SQL uses single quotes around text alues (most database systems !ill also accept doublequotes).

Alt#oug#" numeric alues s#ould not be enclosed in quotes.

=or text alues0

Tis is co""ect

SELECT * FROM %e"sons ,HERE Fi"st'ame./Tove/

Tis is 2"on#

SELECT * FROM %e"sons ,HERE Fi"st'ame.Tove

=or numeric alues0

Tis is co""ect

SELECT * FROM %e"sons ,HERE 3ea".1456

Tis is 2"on#


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SELECT * FROM %e"sons ,HERE 3ea"./1456/

)erators &o2ed in the W1,R, Cause-it# t#e -$&,& clause" t#e follo!ing operators can be used0

Operator Description

. E7ual

89 'ot e7ual

9 :"eate" tan

8 Less tan

9. :"eate" tan o" e7ual

8. Less tan o" e7ual

!ET,EE

'!et2een an inclusive "an#e

L&E Sea"c ;o" a -atte"n

' ; +ou


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#e 6, operator displays a record if eit#er t#e first condition or t#e second condition is true.

&ND )erator ,/a$)e

#e 7*ersons7 table0





No! !e !ant to select only t#e persons !it# t#e first name equal to 7oe7 AN+ t#e last name

equal to 7Sendson70



,HERE Fi"st'ame./Tove/

>' Last'ame./Svendson/




R )erator ,/a$)e

No! !e !ant to select only t#e persons !it# t#e first name equal to 7oe7 6, t#e first name

equal to 76la70



,HERE Fi"st'ame./Tove/

OR Fi"st'ame./Ola/


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Co$bining &ND 3 R

Cou can also combine AN+ and 6, (use parent#esis to form complex expressions).

No! !e !ant to select only t#e persons !it# t#e last name equal to 7Sendson7 AN+ t#e firstname equal to 7oe7 6, to 76la70


SELECT * FROM %e"sons ,HERE

Last'ame./Svendson/

>' (Fi"st'ame./Tove/ OR Fi"st'ame./Ola/)




SQL ORDER !" #ey$ord

#e 6,+&, 1C 3ey!ord is used to sort t#e result2set.

The RD,R BY (e'2ord

#e 6,+&, 1C 3ey!ord is used to sort t#e result2set by a specified column.

#e 6,+&, 1C 3ey!ord sort t#e records in ascending order by default.

If you !ant to sort t#e records in a descending order" you can use t#e +&S' 3ey!ord.


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SQL ORDER !" Syntax


FROM table_name

ORER !3 column_name(s) >SC?ESC

RD,R BY ,/a$)e

#e 7*ersons7 table0





@ 'ilsen Tom Ain#vn $ Stavan#e"

No! !e !ant to select all t#e persons from t#e table aboe" #o!eer" !e !ant to sort t#e persons

by t#eir last name.


SELECT * FROM %e"sons ORER !3 Last'ame







RD,R BY D,SC ,/a$)e


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No! !e !ant to select all t#e persons from t#e table aboe" #o!eer" !e !ant to sort t#e persons

descending by t#eir last name.


SELECT * FROM %e"sonsORER !3 Last'ame ESC







SQL INSERT INTO Statement

#e INS&, IN6 statement is used to insert ne! records in a table.

The #NS,RT #NT State$ent

#e INS&, IN6 statement is used to insert a ne! ro! in a table.

SQL INSERT INTO Syntax

It is possible to !rite t#e INS&, IN6 statement in t!o forms.

#e first form doesnDt specify t#e column names !#ere t#e data !ill be inserted" only t#eir

alues0

'SERT 'TO table_name

A>LBES (value1 value value$)


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#e second form specifies bot# t#e column names and t#e alues to be inserted0

'SERT 'TO table_name (column1 column column$)


SQL #NS,RT #NT ,/a$)e

-e #ae t#e follo!ing 7*ersons7 table0





No! !e !ant to insert a ne! ro! in t#e 7*ersons7 table.

-e use t#e follo!ing SQL statement0

'SERT 'TO %e"sons

A>LBES (@/'ilsen/ /Doan/ /!a


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#e follo!ing SQL statement !ill add a ne! ro!" but only add data in t#e 7*LBES (6 /Tessem/ /Da


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SQL U!D&T, ,/a$)e

#e 7*ersons7 table0





@ 'ilsen Doan !aTE %e"sons

SET >dd"ess./'issestien 5/ Cit+./Sandnes/

,HERE Last'ame./Tessem/ >' Fi"st'ame./Da


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B%>TE %e"sons

SET >dd"ess./'issestien 5/ Cit+./Sandnes/

#e 7*ersons7 table !ould #ae loo3ed li3e t#is0


1 Hansen Ola 'issestien 5 Sandnes

Svendson Tove 'issestien 5 Sandnes

$ %ette"sen &a"i 'issestien 5 Sandnes

@ 'ilsen Doan 'issestien 5 Sandnes

6 Tessem Da


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@ 'ilsen Doan !a


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Note:1e ery careful !#en deleting records. Cou cannot undo t#is statement/

SQL TO Clause

The T! Cause

#e 6* clause is used to specify t#e number of records to return.

#e 6* clause can be ery useful on large tables !it# t#ousands of records. ,eturning a largenumber of records can impact on performance.

Note:Not all database systems support t#e 6* clause.

SQL Ser'er SyntaxSELECT TO% numbe"?-e"cent column_name(s)

FROM table_name

SQL S,L,CT T! ,4ui5aent in M'SQL and ra*e

(ySQL Syntax


FROM table_name

LMT numbe"

Examle

SELECT *

FROM %e"sons

LMT 6

Oracle Syntax


FROM table_name,HERE RO,'BM 8. numbe"

Examle

SELECT *

FROM %e"sons ,HERE RO,'BM 8.6


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SQL T! ,/a$)e

#e 7*ersons7 table0






No! !e !ant to select only t#e t!o first records in t#e table aboe.


SELECT TO% * FROM %e"sons





SQL T! !,RC,NT ,/a$)e

#e 7*ersons7 table0





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No! !e !ant to select only F9 of t#e records in t#e table aboe.


SELECT TO% 60 %ERCE'T * FROM %e"sons





SQL LI#E Oerator

#e LI;& operator is used in a -$&,& clause to searc# for a specified pattern in a column.

The L#(, )erator

#e LI;& operator is used to searc# for a specified pattern in a column.

SQL LI#E Syntax


FROM table_name

,HERE column_name L&E -atte"n

L#(, )erator ,/a$)e

#e 7*ersons7 table0


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No! !e !ant to select t#e persons liing in a city t#at starts !it# 7s7 from t#e table aboe.



,HERE Cit+ L&E /sG/

#e 77 sign can be used to define !ildcards (missing letters in t#e pattern) bot# before andafter t#e pattern.






Next" !e !ant to select t#e persons liing in a city t#at ends !it# an 7s7 from t#e 7*ersons7 table.



,HERE Cit+ L&E /Gs/






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Next" !e !ant to select t#e persons liing in a city t#at contains t#e pattern 7ta7 from t#e

7*ersons7 table.


SELECT * FROM %e"sons,HERE Cit+ L&E /GtavG/




It is also possible to select t#e persons liing in a city t#at N6 contains t#e pattern 7ta7 from

t#e 7*ersons7 table" by using t#e N6 3ey!ord.



,HERE Cit+ 'OT L&E /GtavG/





SQL Wildcards

SQL !ildcards can be used !#en searc#ing for data in a database.

SQL Wid*ards

SQL !ildcards can substitute for one or more c#aracters !#en searc#ing for data in a database.


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SQL !ildcards must be used !it# t#e SQL LI;& operator.

-it# SQL" t#e follo!ing !ildcards can be used0

Wildcard Description

G > substitute ;o" e"o o" mo"e ca"acte"s

_ > substitute ;o" e=actl+ one ca"acte"

Ica"listJ >n+ sin#le ca"acte" in ca"list

IKca"listJ

or

H/c#arlist

>n+ sin#le ca"acte" not in ca"list

SQL Wid*ard ,/a$)es






Using the 6 Wid*ard

No! !e !ant to select t#e persons liing in a city t#at starts !it# 7sa7 from t#e 7*ersons7 table.



,HERE Cit+ L&E /saG/



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Next" !e !ant to select t#e persons liing in a city t#at contains t#e pattern 7nes7 from t#e

7*ersons7 table.



,HERE Cit+ L&E /GnesG/





Using the " Wid*ardNo! !e !ant to select t#e persons !it# a first name t#at starts !it# any c#aracter" follo!ed by7la7 from t#e 7*ersons7 table.



,HERE Fi"st'ame L&E /_la/





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Next" !e !ant to select t#e persons !it# a last name t#at starts !it# 7S7" follo!ed by any

c#aracter" follo!ed by 7end7" follo!ed by any c#aracter" follo!ed by 7on7 from t#e 7*ersons7

table.



,HERE Last'ame L&E /S_end_on/




Using the 7*harist8 Wid*ard

No! !e !ant to select t#e persons !it# a last name t#at starts !it# 7b7 or 7s7 or 7p7 from t#e

7*ersons7 table.



,HERE Last'ame L&E /Ibs-JG/





Next" !e !ant to select t#e persons !it# a last name t#at do not start !it# 7b7 or 7s7 or 7p7 from

t#e 7*ersons7 table.



,HERE Last'ame L&E /Ibs-JG/


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SQL IN Oerator

The #N )erator

#e IN operator allo!s you to specify multiple alues in a -$&,& clause.

SQL IN Syntax


FROM table_name

,HERE column_name ' (value1value)

#N )erator ,/a$)e

#e 7*ersons7 table0





No! !e !ant to select t#e persons !it# a last name equal to 7$ansen7 or 7*ettersen7 from t#etable aboe.



,HERE Last'ame ' (/Hansen//%ette"sen/)


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SQL !ETWEEN Oerator

#e 1&-&&N operator is used in a -$&,& clause to select a range of data bet!een t!o

alues.

The B,TW,,N )erator

#e 1&-&&N operator selects a range of data bet!een t!o alues. #e alues can be

numbers" text" or dates.

SQL !ETWEEN Syntax


FROM table_name

,HERE column_name

!ET,EE' value1 >' value

B,TW,,N )erator ,/a$)e

#e 7*ersons7 table0






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No! !e !ant to select t#e persons !it# a last name alp#abetically bet!een 7$ansen7 and

7*ettersen7 from t#e table aboe.


SELECT * FROM %e"sons,HERE Last'ame

!ET,EE' /Hansen/ >' /%ette"sen/




Note:#e 1&-&&N operator is treated differently in different databases.

In some databases" persons !it# t#e LastName of 7$ansen7 or 7*ettersen7 !ill not be listed"

because t#e 1&-&&N operator only selects fields t#at are bet!een and excluding t#e testalues).

In ot#er databases" persons !it# t#e LastName of 7$ansen7 or 7*ettersen7 !ill be listed" because

t#e 1&-&&N operator selects fields t#at are bet!een and including t#e test alues).

And in ot#er databases" persons !it# t#e LastName of 7$ansen7 !ill be listed" but 7*ettersen7!ill not be listed (li3e t#e example aboe)" because t#e 1&-&&N operator selects fields

bet!een t#e test alues" including t#e first test alue and excluding t#e last test alue.

#erefore0 '#ec3 #o! your database treats t#e 1&-&&N operator.

,/a$)e 9

o display t#e persons outside t#e range in t#e preious example" use N6 1&-&&N0


,HERE Last'ame'OT !ET,EE' /Hansen/ >' /%ette"sen/




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SQL Alias

-it# SQL" an alias name can be gien to a table or to a column.

SQL &ias

Cou can gie a table or a column anot#er name by using an alias. #is can be a good t#ing to doif you #ae ery long or complex table names or column names.

An alias name could be anyt#ing" but usually it is s#ort.

SQL Alias Syntax )or Ta*les


FROM table_name

>S alias_name

SQL Alias Syntax )or ColumnsSELECT column_name >S alias_name

FROM table_name

&ias ,/a$)e

Assume !e #ae a table called 7*ersons7 and anot#er table called 7*roductS -


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%"oduct_O"de"s >S -o

,HERE -Last'ame./Hansen/ >' -Fi"st'ame./Ola/

#e same S&L&' statement !it#out aliases0

SELECT %"oduct_O"de"sO"de" %e"sonsLast'ame %e"sonsFi"st'ame

FROM %e"sons

%"oduct_O"de"s

,HERE %e"sonsLast'ame./Hansen/ >' %e"sonsFi"st'ame./Ola/

As youDll see from t#e t!o S&L&' statements aboeJ aliases can ma3e queries easier to bot#!rite and to read.

SQL +oins

SQL %oins are used to query data from t!o or more tables" based on a relations#ip bet!een

certain columns in t#ese tables.

SQL #N

#e E6IN 3ey!ord is used in an SQL statement to query data from t!o or more tables" based on

a relations#ip bet!een certain columns in t#ese tables.

ables in a database are often related to eac# ot#er !it# 3eys.

A primary 3ey is a column (or a combination of columns) !it# a unique alue for eac# ro!.

&ac# primary 3ey alue must be unique !it#in t#e table. #e purpose is to bind data toget#er"

across tables" !it#out repeating all of t#e data in eery table.

Loo3 at t#e 7*ersons7 table0






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Note t#at t#e 7*


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SQL INNER +OIN Syntax


FROM table_name1

''ER DO' table_name

O' table_name1column_name.table_namecolumn_name

!S:INN&, E6IN is t#e same as E6IN.

SQL #NN,R #N ,/a$)e

#e 7*ersons7 table0





#e 76rders7 table0

O_Id OrderNo P_Id

1 46 $

@@5 $

$ @65 1

@ @65 1

6 $@5@ 16

No! !e !ant to list all t#e persons !it# any orders.


SELECT %e"sonsLast'ame %e"sonsFi"st'ame O"de"sO"de"'o

FROM %e"sons

''ER DO' O"de"s

O' %e"sons%_d.O"de"s%_d


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ORER !3 %e"sonsLast'ame


LastName FirstName OrderNo

Hansen Ola @65

Hansen Ola @65

%ette"sen &a"i 46

%ette"sen &a"i @@5

#e INN&, E6IN 3ey!ord return ro!s !#en t#ere is at least one matc# in bot# tables. If t#ere

are ro!s in 7*ersons7 t#at do not #ae matc#es in 76rders7" t#ose ro!s !ill N6 be listed.

SQL LE,T +OIN #ey$ord

SQL L,%T #N (e'2ord

#e L&= E6IN 3ey!ord returns all ro!s from t#e left table (table


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#e 76rders7 table0

O_Id OrderNo P_Id

1 46 $

@@5 $

$ @65 1

@ @65 1

6 $@5@ 16

No! !e !ant to list all t#e persons and t#eir orders 2 if any" from t#e tables aboe.



FROM %e"sons

LEFT DO' O"de"sO' %e"sons%_d.O"de"s%_d




Hansen Ola @65

Hansen Ola @65

%ette"sen &a"i 46

%ette"sen &a"i @@5

Svendson Tove


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#e L&= E6IN 3ey!ord returns all t#e ro!s from t#e left table (*ersons)" een if t#ere are no

matc#es in t#e rig#t table (6rders).

SQL RI-HT +OIN #ey$ord

SQL R#;1T #N (e'2ord

#e ,IG$ E6IN 3ey!ord ,eturn all ro!s from t#e rig#t table (table


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@ @65 1

6 $@5@ 16

No! !e !ant to list all t#e orders !it# containing persons 2 if any" from t#e tables aboe.



FROM %e"sons

R:HT DO' O"de"s





Hansen Ola @65

Hansen Ola @65

%ette"sen &a"i 46

%ette"sen &a"i @@5

$@5@

#e ,IG$ E6IN 3ey!ord returns all t#e ro!s from t#e rig#t table (6rders)" een if t#ere are no

matc#es in t#e left table (*ersons).

SQL ,%LL +OIN #ey$ord

SQL %ULL #N (e'2ord#e =LL E6IN 3ey!ord return ro!s !#en t#ere is a matc# in one of t#e tables.

SQL ,%LL +OIN Syntax


FROM table_name1


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FBLL DO' table_name

O' table_name1column_name.table_namecolumn_name

SQL %ULL #N ,/a$)e

#e 7*ersons7 table0





#e 76rders7 table0

O_Id OrderNo P_Id

1 46 $

@@5 $

$ @65 1

@ @65 1

6 $@5@ 16

No! !e !ant to list all t#e persons and t#eir orders" and all t#e orders !it# t#eir persons.



FROM %e"sonsFBLL DO' O"de"s





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Hansen Ola @65

Hansen Ola @65

%ette"sen &a"i 46

%ette"sen &a"i @@5

Svendson Tove

$@5@

#e =LL E6IN 3ey!ord returns all t#e ro!s from t#e left table (*ersons)" and all t#e ro!s fromt#e rig#t table (6rders). If t#ere are ro!s in 7*ersons7 t#at do not #ae matc#es in 76rders7" or if

t#ere are ro!s in 76rders7 t#at do not #ae matc#es in 7*ersons7" t#ose ro!s !ill be listed as!ell.

SQL %NION Oerator

#e SQL NI6N operator combines t!o or more S&L&' statements.

The SQL UN#N )erator

#e NI6N operator is used to combine t#e result2set of t!o or more S&L&' statements.

Notice t#at eac# S&L&' statement !it#in t#e NI6N must #ae t#e same number of columns.

#e columns must also #ae similar data types. Also" t#e columns in eac# S&L&' statement

must be in t#e same order.

SQL %NION Syntax

SELECT column_name(s) FROM table_name1

B'O'SELECT column_name(s) FROM table_name

Note:#e NI6N operator selects only distinct alues by default. o allo! duplicate alues"

use NI6N ALL.


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SQL %NION ALL Syntax

SELECT column_name(s) FROM table_name1

B'O' >LL

SELECT column_name(s) FROM table_name

!S:#e column names in t#e result2set of a NI6N are al!ays equal to t#e column names in t#e

first S&L&' statement in t#e NI6N.

SQL UN#N ,/a$)e

Loo3 at t#e follo!ing tables0


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SELECT E_'ame FROM Em-lo+ees_BS>


E_Name

Hansen Ola

Svendson Tove

Svendson Ste-en

%ette"sen &a"i

Tu"ne" Sall+

&ent Cla"LL

SELECT E_'ame FROM Em-lo+ees_BS>

Resut

E_Name

Hansen Ola

Svendson Tove

Svendson Ste-en

%ette"sen &a"i


42/107

Tu"ne" Sall+

&ent Cla"!LE %e"sons

(

%_d int

Last'ame va"ca"(66)

Fi"st'ame va"ca"(66)

>dd"ess va"ca"(66)

Cit+ va"ca"(66)

)

#e *


46/107

'onstraints are used to limit t#e type of data t#at can go into a table.

'onstraints can be specified !#en a table is created (!it# t#e ',&A& A1L& statement) or

after t#e table is created (!it# t#e AL&, A1L& statement).

-e !ill focus on t#e follo!ing constraints0

'OT 'BLL

B'NBE

%RM>R3 &E3

FORE:' &E3

CHEC&

EF>BLT

#e next c#apters !ill describe eac# constraint in details.

SQL NOT N%LL Constraint

1y default" a table column can #old NLL alues.

SQL NT NULL Constraint#e N6 NLL constraint enforces a column to N6 accept NLL alues.

#e N6 NLL constraint enforces a field to al!ays contain a alue. #is means t#at you

cannot insert a ne! record" or update a record !it#out adding a alue to t#is field.

#e follo!ing SQL enforces t#e 7*TE T>!LE %e"sons

(%_d int 'OT 'BLL

Last'ame va"ca"(66) 'OT 'BLL


>dd"ess va"ca"(66)

Cit+ va"ca"(66)

)


47/107

SQL %NIQ%E Constraint

SQL UN#QU, Constraint#e NIQ& constraint uniquely identifies eac# record in a database table.

#e NIQ& and *,IA,C ;&C constraints bot# proide a guarantee for uniqueness for a

column or set of columns.

A *,IA,C ;&C constraint automatically #as a NIQ& constraint defined on it.

Note t#at you can #ae many NIQ& constraints per table" but only one *,IA,C ;&C

constraint per table.

SQL UN#QU, Constraint on CR,&T, T&BL,

#e follo!ing SQL creates a NIQ& constraint on t#e 7*dd"ess va"ca"(66)

Cit+ va"ca"(66)


48/107

)

o allo! naming of a NIQ& constraint" and for defining a NIQ& constraint on multiplecolumns" use t#e follo!ing SQL syntax0

M'SQL > SQL Ser5er > ra*e > MS &**ess:

CRE>TE T>!LE %e"sons

(

%_d int 'OT 'BLL



>dd"ess va"ca"(66)

Cit+ va"ca"(66)

CO'STR>'T uc_%e"son B'NBE (%_dLast'ame)

)

SQL UN#QU, Constraint on &LT,R T&BL,

o create a NIQ& constraint on t#e 7* B'NBE (%_d)

o allo! naming of a NIQ& constraint" and for defining a NIQ& constraint on multiplecolumns" use t#e follo!ing SQL syntax0


>LTER T>!LE %e"sons

> CO'STR>'T uc_%e"son B'NBE (%_dLast'ame)

To DR! a UN#QU, Constraint

o drop a NIQ& constraint" use t#e follo!ing SQL0


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M'SQL:

>LTER T>!LE %e"sons

RO% 'E uc_%e"son

SQL Ser5er > ra*e > MS &**ess:

>LTER T>!LE %e"sons

RO% CO'STR>'T uc_%e"son

SQL RI(AR" #E" Constraint

SQL !R#M&RY (,Y Constraint

#e *,IA,C ;&C constraint uniquely identifies eac# record in a database table.

*rimary 3eys must contain unique alues.

A primary 3ey column cannot contain NLL alues.

&ac# table s#ould #ae a primary 3ey" and eac# table can #ae only 6N& primary 3ey.

SQL !R#M&RY (,Y Constraint on CR,&T, T&BL,

#e follo!ing SQL creates a *,IA,C ;&C on t#e 7*R3 &E3 (%_d)

)


50/107



(

%_d int 'OT 'BLL %RM>R3 &E3

Last'ame va"ca"(66) 'OT 'BLLFi"st'ame va"ca"(66)

>dd"ess va"ca"(66)

Cit+ va"ca"(66)

)

o allo! naming of a *,IA,C ;&C constraint" and for defining a *,IA,C ;&C constraint

on multiple columns" use t#e follo!ing SQL syntax0



(

%_d int 'OT 'BLL



>dd"ess va"ca"(66)

Cit+ va"ca"(66)

CO'STR>'T - SQL Ser5er > ra*e > MS &**ess:


51/107

>LTER T>!LE %e"sons

> CO'STR>'T -R3 &E3


>LTER T>!LE %e"sons

RO% CO'STR>'T -


52/107

O_Id OrderNo P_Id

1 46 $

@@5 $

$ @65

@ @65 1

Note t#at t#e 7* ra*e > MS &**ess:

CRE>TE T>!LE O"de"s

(


53/107

O_d int 'OT 'BLL %RM>R3 &E3

O"de"'o int 'OT 'BLL

%_d int FORE:' &E3 REFERE'CES %e"sons(%_d)

)

o allo! naming of a =6,&IGN ;&C constraint" and for defining a =6,&IGN ;&C constraint

on multiple columns" use t#e follo!ing SQL syntax0


CRE>TE T>!LE O"de"s

(

O_d int 'OT 'BLL


%_d int

%RM>R3 &E3 (O_d)CO'STR>'T ;'T ;


54/107

To DR! a %R,#;N (,Y Constraint

o drop a =6,&IGN ;&C constraint" use t#e follo!ing SQL0

M'SQL:

>LTER T>!LE O"de"s

RO% FORE:' &E3 ;


55/107



>dd"ess va"ca"(66)

Cit+ va"ca"(66)

CHEC& (%_d90)

)



(

%_d int 'OT 'BLL CHEC& (%_d90)



>dd"ess va"ca"(66)

Cit+ va"ca"(66))

o allo! naming of a '$&'; constraint" and for defining a '$&'; constraint on multiple

columns" use t#e follo!ing SQL syntax0



(

%_d int 'OT 'BLL



>dd"ess va"ca"(66)

Cit+ va"ca"(66)

CO'STR>'T c


56/107

> CHEC& (%_d90)

o allo! naming of a '$&'; constraint" and for defining a '$&'; constraint on multiplecolumns" use t#e follo!ing SQL syntax0


>LTER T>!LE %e"sons

> CO'STR>'T c ra*e > MS &**ess:

>LTER T>!LE %e"sons

RO% CO'STR>'T c SQL Ser5er > ra*e > MS &**ess:


(

%_d int 'OT 'BLL


57/107



>dd"ess va"ca"(66)

Cit+ va"ca"(66) EF>BLT /Sandnes/

)

#e +&=AL constraint can also be used to insert system alues" by using functions li3e

G&+A&()0

CRE>TE T>!LE O"de"s

(

O_d int 'OT 'BLL


%_d int

O"de"ate date EF>BLT :ET>TE()

)

SQL D,%&ULT Constraint on &LT,R T&BL,

o create a +&=AL constraint on t#e 7'ity7 column !#en t#e table is already created" use t#efollo!ing SQL0

M'SQL:

>LTER T>!LE %e"sons

>LTER Cit+ SET EF>BLT /S>''ES/


>LTER T>!LE %e"sons

>LTER COLBM' Cit+ SET EF>BLT /S>''ES/

To DR! a D,%&ULT Constraint

o drop a +&=AL constraint" use t#e follo!ing SQL0

M'SQL:


58/107

>LTER T>!LE %e"sons

>LTER Cit+ RO% EF>BLT


>LTER T>!LE %e"sons

>LTER COLBM' Cit+ RO% EF>BLT

SQL CREATE INDE. Statement

#e ',&A& IN+&K statement is used to create indexes in tables.

Indexes allo! t#e database application to find data fastJ !it#out reading t#e !#ole table.

#nde/es

An index can be created in a table to find data more quic3ly and efficiently.

#e users cannot see t#e indexes" t#ey are %ust used to speed up searc#es4queries.

Note:pdating a table !it# indexes ta3es more time t#an updating a table !it#out (because t#eindexes also need an update). So you s#ould only create indexes on columns (and tables) t#at

!ill be frequently searc#ed against.

SQL CREATE INDE. Syntax

'reates an index on a table. +uplicate alues are allo!ed0

CRE>TE 'E inde=_name

O' table_name (column_name)

SQL CREATE %NIQ%E INDE. Syntax

'reates a unique index on a table. +uplicate alues are not allo!ed0

CRE>TE B'NBE 'E inde=_name



59/107

Note:#e syntax for creating indexes aries amongst different databases. #erefore0 '#ec3 t#e

syntax for creating indexes in your database.

CR,&T, #ND, ,/a$)e

#e SQL statement belo! creates an index named 7*Index7 on t#e 7LastName7 column in t#e7*ersons7 table0

CRE>TE 'E %nde=

O' %e"sons (Last'ame)

If you !ant to create an index on a combination of columns" you can list t#e column names!it#in t#e parent#eses" separated by commas0

CRE>TE 'E %nde=O' %e"sons (Last'ame Fi"st'ame)

SQL DRO INDE./ DRO TA!LE/ and DRO DATA!ASE

Indexes" tables" and databases can easily be deleted4remoed !it# t#e +,6* statement.

The DR! #ND, State$ent

#e +,6* IN+&K statement is used to delete an index in a table.

DRO INDE. Syntax )or (S Access0

RO% 'E inde=_name O' table_name

DRO INDE. Syntax )or (S SQL Ser'er0

RO% 'E table_nameinde=_name

DRO INDE. Syntax )or D!12Oracle0

RO% 'E inde=_name

DRO INDE. Syntax )or (ySQL0

>LTER T>!LE table_name RO% 'E inde=_name


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The DR! T&BL, State$ent#e +,6* A1L& statement is used to delete a table.

RO% T>!LE table_name

The DR! D&T&B&S, State$ent

#e +,6* +AA1AS& statement is used to delete a database.

RO% >T>!>SE database_name

The TRUNC&T, T&BL, State$ent

-#at if !e only !ant to delete t#e data inside t#e table" and not t#e table itself

#en" use t#e ,N'A& A1L& statement0

TRB'C>TE T>!LE table_name

SQL ALTER TA!LE Statement

The &LT,R T&BL, State$ent

#e AL&, A1L& statement is used to add" delete" or modify columns in an existing table.

SQL ALTER TA!LE Syntax

o add a column in a table" use t#e follo!ing syntax0

>LTER T>!LE table_name


61/107

> column_name datat+-e

o delete a column in a table" use t#e follo!ing syntax (notice t#at some database systems donDtallo! deleting a column)0


RO% COLBM' column_name

o c#ange t#e data type of a column in a table" use t#e follo!ing syntax0


>LTER COLBM' column_name datat+-e

SQL &LT,R T&BL, ,/a$)e

Loo3 at t#e 7*ersons7 table0





No! !e !ant to add a column named 7+ate6f1irt#7 in t#e 7*ersons7 table.


>LTER T>!LE %e"sons

> ateO;!i"t date

Notice t#at t#e ne! column" 7+ate6f1irt#7" is of type date and is going to #old a date. #e datatype specifies !#at type of data t#e column can #old. =or a complete reference of all t#e data

types aailable in S Access" ySQL" and SQL Serer" go to our complete +ata ypesreference.

#e 7*ersons7 table !ill no! li3e t#is0

P_Id LastName FirstName Address City DateO"#irt$
http://www.w3schools.com/sql/sql_datatypes.asphttp://www.w3schools.com/sql/sql_datatypes.asphttp://www.w3schools.com/sql/sql_datatypes.asphttp://www.w3schools.com/sql/sql_datatypes.asp


62/107




Change Data T')e ,/a$)e

No! !e !ant to c#ange t#e data type of t#e column named 7+ate6f1irt#7 in t#e 7*ersons7 table.


>LTER T>!LE %e"sons

>LTER COLBM' ateO;!i"t +ea"

Notice t#at t#e 7+ate6f1irt#7 column is no! of type year and is going to #old a year in a t!o2digit or four2digit format.

DR! CLUMN ,/a$)e

Next" !e !ant to delete t#e column named 7+ate6f1irt#7 in t#e 7*ersons7 table.


>LTER T>!LE %e"sons

RO% COLBM' ateO;!i"t

#e 7*ersons7 table !ill no! li3e t#is0






63/107

SQL A%TO INCRE(ENT ,ield

Auto2increment allo!s a unique number to be generated !#en a ne! record is inserted into a

table.

&UT #NCR,M,NT a %ied

Mery often !e !ould li3e t#e alue of t#e primary 3ey field to be created automatically eerytime a ne! record is inserted.

-e !ould li3e to create an auto2increment field in a table.

S'nta/ +or M'SQL

#e follo!ing SQL statement defines t#e 7*TE T>!LE %e"sons

(

%_d int 'OT 'BLL >BTO_'CREME'T


Fi"st'ame va"ca"(66)>dd"ess va"ca"(66)

Cit+ va"ca"(66)

%RM>R3 &E3 (%_d)

)

ySQL uses t#e A6LTER T>!LE %e"sons >BTO_'CREME'T.100


64/107

o insert a ne! record into t#e 7*ersons7 table" !e !ill not #ae to specify a alue for t#e 7*LBES (/La"s//Monsen/)

#e SQL statement aboe !ould insert a ne! record into t#e 7*ersons7 table. #e 7*dd"ess va"ca"(66)

Cit+ va"ca"(66)

)

#e S SQL Serer uses t#e I+&NIC 3ey!ord to perform an auto2increment feature.

1y default" t#e starting alue for I+&NIC is 8" and it !ill increment by 8 for eac# ne! record.

o specify t#at t#e 7*


65/107


66/107

M'A>LBE 1

ST>RT ,TH 1

'CREME'T !3 1

C>CHE 10

#e code aboe creates a sequence ob%ect called seqTE AE, vie2_name >S


FROM table_name


67/107

,HERE condition

Note:A ie! al!ays s#o!s up2to2date data/ #e database engine recreates t#e data" using t#eie!Ds SQL statement" eery time a user queries a ie!.

SQL CR,&T, #,W ,/a$)es

If you #ae t#e Nort#!ind database you can see t#at it #as seeral ie!s installed by default.

#e ie! 7'urrent *roduct List7 lists all actie products (products t#at are not discontinued)

from t#e 7*roducts7 table. #e ie! is created !it# t#e follo!ing SQL0

CRE>TE AE, ICu""ent %"oduct ListJ >S

SELECT %"oduct%"oduct'ame

FROM %"oducts,HERE iscontinued.'o

-e can query t#e ie! aboe as follo!s0

SELECT * FROM ICu""ent %"oduct ListJ

Anot#er ie! in t#e Nort#!ind sample database selects eery product in t#e 7*roducts7 table

!it# a unit price #ig#er t#an t#e aerage unit price0

CRE>TE AE, I%"oducts >bove >ve"a#e %"iceJ >S

SELECT %"oduct'ameBnit%"ice

FROM %"oducts

,HERE Bnit%"ice9(SELECT >A:(Bnit%"ice) FROM %"oducts)


SELECT * FROM I%"oducts >bove >ve"a#e %"iceJ

Anot#er ie! in t#e Nort#!ind database calculates t#e total sale for eac# category in 8O. Notet#at t#is ie! selects its data from anot#er ie! called 7*roduct Sales for 8O70

CRE>TE AE, ICate#o"+ Sales Fo" 144J >S

SELECT ST'CT Cate#o"+'ameSum(%"oductSales) >S Cate#o"+Sales

FROM I%"oduct Sales ;o" 144J

:ROB% !3 Cate#o"+'ame


68/107


SELECT * FROM ICate#o"+ Sales Fo" 144J

-e can also add a condition to t#e query. No! !e !ant to see t#e total sale only for t#e category

71eerages70

SELECT * FROM ICate#o"+ Sales Fo" 144J

,HERE Cate#o"+'ame./!eve"a#es/

SQL U)dating a ie2

Cou can update a ie! by using t#e follo!ing syntax0

SQL CREATE OR RELACE 3IEW Syntax

CRE>TE OR RE%L>CE AE, vie2_name >S


FROM table_name

,HERE condition

No! !e !ant to add t#e 7'ategory7 column to t#e 7'urrent *roduct List7 ie!. -e !ill update

t#e ie! !it# t#e follo!ing SQL0

CRE>TE AE, ICu""ent %"oduct ListJ >S

SELECT %"oduct%"oduct'ameCate#o"+

FROM %"oducts

,HERE iscontinued.'o

SQL Dro))ing a ie2

Cou can delete a ie! !it# t#e +,6* MI&- command.

SQL DRO 3IEW Syntax

RO% AE, vie2_name


69/107

SQL Date ,unctions

SQL Dates#e most difficult part !#en !or3ing !it# dates is to be sure t#at t#e format of t#e date you

are trying to insert" matc#es t#e format of t#e date column in t#e database.

As long as your data contains only t#e date portion" your queries !ill !or3 as expected.$o!eer" if a time portion is inoled" it gets complicated.

1efore tal3ing about t#e complications of querying for dates" !e !ill loo3 at t#e most important

built2in functions for !or3ing !it# dates.

M'SQL Date %un*tions

#e follo!ing table lists t#e most important built2in date functions in ySQL0

F%nction Description

'O,() Retu"ns te cu""ent date and time

CBR>TE() Retu"ns te cu""ent date

CBRTME() Retu"ns te cu""ent time

>TE() E=t"acts te date -a"t o; a date o" datePtime e=-"ession

ETR>CT() Retu"ns a sin#le -a"t o; a datePtime

>TE_>() >dds a s-eci;ied time inte"val to a date

>TE_SB!() Subt"acts a s-eci;ied time inte"val ;"om a date

>TEFF() Retu"ns te numbe" o; da+s bet2een t2o dates

>TE_FORM>T() is-la+s datePtime data in di;;e"ent ;o"mats

SQL Ser5er Date %un*tions
http://www.w3schools.com/sql/func_now.asphttp://www.w3schools.com/sql/func_curdate.asphttp://www.w3schools.com/sql/func_curtime.asphttp://www.w3schools.com/sql/func_date.asphttp://www.w3schools.com/sql/func_extract.asphttp://www.w3schools.com/sql/func_date_add.asphttp://www.w3schools.com/sql/func_date_sub.asphttp://www.w3schools.com/sql/func_datediff_mysql.asphttp://www.w3schools.com/sql/func_date_format.asphttp://www.w3schools.com/sql/func_now.asphttp://www.w3schools.com/sql/func_curdate.asphttp://www.w3schools.com/sql/func_curtime.asphttp://www.w3schools.com/sql/func_date.asphttp://www.w3schools.com/sql/func_extract.asphttp://www.w3schools.com/sql/func_date_add.asphttp://www.w3schools.com/sql/func_date_sub.asphttp://www.w3schools.com/sql/func_datediff_mysql.asphttp://www.w3schools.com/sql/func_date_format.asp


70/107

#e follo!ing table lists t#e most important built2in date functions in SQL Serer0

F%nction Description

:ET>TE() Retu"ns te cu""ent date and time

>TE%>RT() Retu"ns a sin#le -a"t o; a datePtime

>TE>() >dds o" subt"acts a s-eci;ied time inte"val ;"om a date

>TEFF() Retu"ns te time bet2een t2o dates

CO'AERT() is-la+s datePtime data in di;;e"ent ;o"mats

SQL Date Data T')es

M'SQLcomes !it# t#e follo!ing data types for storing a date or a date4time alue in t#e

database0

>TE Q ;o"mat 3333QMMQ

>TETME Q ;o"mat 3333QMMQ HHMMSS

TMEST>M% Q ;o"mat 3333QMMQ HHMMSS

3E>R Q ;o"mat 3333 o" 33

SQL Ser5ercomes !it# t#e follo!ing data types for storing a date or a date4time alue in t#edatabase0

>TE Q ;o"mat 3333QMMQ

>TETME Q ;o"mat 3333QMMQ HHMMSS

SM>LL>TETME Q ;o"mat 3333QMMQ HHMMSS

TMEST>M% Q ;o"mat a uni7ue numbe"

Note:#e date types are c#osen for a column !#en you create a ne! table in your database/

=or an oerie! of all data types aailable" go to our complete +ata ypes reference.

SQL Wor=ing 2ith Dates

Cou can compare t!o dates easily if t#ere is no time component inoled/
http://www.w3schools.com/sql/func_getdate.asphttp://www.w3schools.com/sql/func_datepart.asphttp://www.w3schools.com/sql/func_dateadd.asphttp://www.w3schools.com/sql/func_datediff.asphttp://www.w3schools.com/sql/func_convert.asphttp://www.w3schools.com/sql/sql_datatypes.asphttp://www.w3schools.com/sql/sql_datatypes.asphttp://www.w3schools.com/sql/sql_datatypes.asphttp://www.w3schools.com/sql/func_getdate.asphttp://www.w3schools.com/sql/func_datepart.asphttp://www.w3schools.com/sql/func_dateadd.asphttp://www.w3schools.com/sql/func_datediff.asphttp://www.w3schools.com/sql/func_convert.asphttp://www.w3schools.com/sql/sql_datatypes.asp


71/107

Assume !e #ae t#e follo!ing 76rders7 table0

OrderId Prod%ctName OrderDate

1 :eitost 00Q11Q11

Camembe"t %ie""ot 00Q11Q04

$ Moa"ella di :iovanni 00Q11Q11

@ Masca"-one Fabioli 00Q10Q4

No! !e !ant to select t#e records !it# an 6rder+ate of 7599P2882887 from t#e table aboe.


SELECT * FROM O"de"s ,HERE O"de"ate./00Q11Q11/



1 :eitost 00Q11Q11

$ Moa"ella di :iovanni 00Q11Q11

No!" assume t#at t#e 76rders7 table loo3s li3e t#is (notice t#e time component in t#e

76rder+ate7 column)0


1 :eitost 00Q11Q11 1$$@@

Camembe"t %ie""ot 00Q11Q04 16@61

$ Moa"ella di :iovanni 00Q11Q11 11101

@ Masca"-one Fabioli 00Q10Q4 1@6564

If !e use t#e same S&L&' statement as aboe0

SELECT * FROM O"de"s ,HERE O"de"ate./00Q11Q11/


72/107

!e !ill get no result/ #is is because t#e query is loo3ing only for dates !it# no time portion.

Ti):If you !ant to 3eep your queries simple and easy to maintain" do not allo! time

components in your dates/

SQL N%LL 3alues

NLL alues represent missing un3no!n data.

1y default" a table column can #old NLL alues.

#is c#apter !ill explain t#e IS NLL and IS N6 NLL operators.

SQL NULL aues

If a column in a table is optional" !e can insert a ne! record or update an existing record !it#out

adding a alue to t#is column. #is means t#at t#e field !ill be saed !it# a NLL alue.

NLL alues are treated differently from ot#er alues.

NLL is used as a place#older for un3no!n or inapplicable alues.

Note:It is not possible to compare NLL and 9J t#ey are not equialent.

SQL Wor=ing 2ith NULL aues

Loo3 at t#e follo!ing 7*ersons7 table0


1 Hansen Ola Sandnes


$ %ette"sen &a"i Stavan#e"

Suppose t#at t#e 7Address7 column in t#e 7*ersons7 table is optional. #is means t#at if !e

insert a record !it# no alue for t#e 7Address7 column" t#e 7Address7 column !ill be saed !it#

a NLL alue.


73/107

$o! can !e test for NLL alues

It is not possible to test for NLL alues !it# comparison operators" suc# as " ?" or ?@.

-e !ill #ae to use t#e IS NLL and IS N6 NLL operators instead.

SQL #S NULL

$o! do !e select only t#e records !it# NLL alues in t#e 7Address7 column

-e !ill #ae to use t#e IS NLL operator0

SELECT Last'ameFi"st'ame>dd"ess FROM %e"sons

,HERE >dd"ess S 'BLL


LastName FirstName Address

Hansen Ola

%ette"sen &a"i

Ti):Al!ays use IS NLL to loo3 for NLL alues.

SQL #S NT NULL

$o! do !e select only t#e records !it# no NLL alues in t#e 7Address7 column

-e !ill #ae to use t#e IS N6 NLL operator0

SELECT Last'ameFi"st'ame>dd"ess FROM %e"sons

,HERE >dd"ess S 'OT 'BLL


LastName FirstName Address

Svendson Tove !o"#vn $


74/107

In t#e next c#apter !e !ill loo3 at t#e ISNLL()" NML()" I=NLL() and '6AL&S'&()

functions.

SQL N%LL ,unctions

SQL #SNULL@A NL@A #%NULL@A and C&L,SC,@A

%un*tions

Loo3 at t#e follo!ing 7*roducts7 table0

P_Id Prod%ctName !nitPrice !nitsIn&toc' !nitsOnOrder

1 Da"lsbe"# 10@6 15 16

Masca"-one $65 $

$ :o"#onola 165 4 0

Suppose t#at t#e 7nits6n6rder7 column is optional" and may contain NLL alues.

-e #ae t#e follo!ing S&L&' statement0

SELECT %"oduct'ameBnit%"ice*(BnitsnStoc


75/107

ra*e

6racle does not #ae an ISNLL() function. $o!eer" !e can use t#e NML() function to

ac#iee t#e same result0

SELECT %"oduct'ameBnit%"ice*(BnitsnStocllo2s 2ole numbe"s ;"om 0 to 66 1 b+te


76/107

nte#e" >llo2s 2ole numbe"s bet2een Q$5 and $5 b+tes

Lon# >llo2s 2ole numbe"s bet2een Q1@@$5@ and 1@@$5@ @ b+tes

Sin#le Sin#le -"ecision ;loatin#Q-oint ,ill andle most decimals @ b+tes

ouble ouble -"ecision ;loatin#Q-oint ,ill andle most decimals b+tes

Cu""enc+ Bse ;o" cu""enc+ Holds u- to 16 di#its o; 2ole dolla"s -lus @

decimal -laces Tip)3ou can coose 2ic count"+/s cu""enc+ to

use

b+tes

>uto'umbe" >uto'umbe" ;ields automaticall+ #ive eac "eco"d its o2n numbe"

usuall+ sta"tin# at 1

@ b+tes

atePTime Bse ;o" dates and times b+tes

3esP'o > lo#ical ;ield can be dis-la+ed as 3esP'o T"uePFalse o" OnPO;;

n code use te constants T"ue and False (e7uivalent to Q1 and 0)

Note)'ull values a"e not allo2ed in 3esP'o ;ields

1 bit

Ole Obect Can sto"e -ictu"es audio video o" ote" !LO!s (!ina"+ La"#e

O!ects)

u- to

1:!

H+-e"lin< Contain lin


77/107

ca"acte"s) Te ma=imum sie is s-eci;ied in -a"entesis Can sto"e u- to

66 ca"acte"s Note); +ou -ut a #"eate" value tan 66 it 2ill be conve"ted

to a TET t+-e

T'3TET Holds a st"in# 2it a ma=imum len#t o; 66 ca"acte"s

TET Holds a st"in# 2it a ma=imum len#t o; 566$6 ca"acte"s

!LO! Fo" !LO!s (!ina"+ La"#e O!ects) Holds u- to 566$6 b+tes o; data

MEBMTET Holds a st"in# 2it a ma=imum len#t o; 1516 ca"acte"s

MEBM!LO! Fo" !LO!s (!ina"+ La"#e O!ects) Holds u- to 1516 b+tes o; data

LO':TET Holds a st"in# 2it a ma=imum len#t o; @4@4546 ca"acte"s

LO':!LO! Fo" !LO!s (!ina"+ La"#e O!ects) Holds u- to @4@4546 b+tes o; data

E'BM(=+etc) Let +ou ente" a list o; -ossible values 3ou can list u- to 566$6 values in an

E'BM list ; a value is inse"ted tat is not in te list a blan< value 2ill be

inse"ted

Note:#e alues are sorted in t#e order you enter t#em.

Cou enter t#e possible alues in t#is format0 &N(DKD"DCD"DRD)

SET Simila" to E'BM e=ce-t tat SET ma+ contain u- to 5@ list items and can

sto"e mo"e tan one coice

Nu$ber t')es:

Data type Description

T'3'T(sie) Q1 to 1 no"mal 0 to 66 B'S:'E* Te ma=imum numbe" o; di#its

ma+ be s-eci;ied in -a"entesis

SM>LL'T(sie) Q$5 to $5 no"mal 0 to 566$6 B'S:'E* Te ma=imum numbe" o;

di#its ma+ be s-eci;ied in -a"entesis

MEBM'T(sie) Q$50 to $50 no"mal 0 to 1516 B'S:'E* Te ma=imumnumbe" o; di#its ma+ be s-eci;ied in -a"entesis

'T(sie) Q1@@$5@ to 1@@$5@ no"mal 0 to @4@4546 B'S:'E* Te

ma=imum numbe" o; di#its ma+ be s-eci;ied in -a"entesis

!:'T(sie) Q4$$0$56@60 to 4$$0$56@60 no"mal 0 to

1@@5@@0$04661516 B'S:'E* Te ma=imum numbe" o; di#its ma+


78/107

be s-eci;ied in -a"entesis

FLO>T(sied) > small numbe" 2it a ;loatin# decimal -oint Te ma=imum numbe" o; di#its

ma+ be s-eci;ied in te sie -a"amete" Te ma=imum numbe" o; di#its to te

"i#t o; te decimal -oint is s-eci;ied in te d -a"amete"

OB!LE(sied) > la"#e numbe" 2it a ;loatin# decimal -oint Te ma=imum numbe" o; di#its

ma+ be s-eci;ied in te sie -a"amete" Te ma=imum numbe" o; di#its to te

"i#t o; te decimal -oint is s-eci;ied in te d -a"amete"

ECM>L(sied) > OB!LE sto"ed as a st"in# allo2in# ;o" a ;i=ed decimal -oint Te

ma=imum numbe" o; di#its ma+ be s-eci;ied in te sie -a"amete" Te

ma=imum numbe" o; di#its to te "i#t o; te decimal -oint is s-eci;ied in te

d -a"amete"

>#e integer types #ae an extra option called NSIGN&+. Normally" t#e integer goes from annegatie to positie alue. Adding t#e NSIGN&+ attribute !ill moe t#at range up so it starts

at ero instead of a negatie number.

Date t')es:


>TE() > date Fo"mat 3333QMMQ

Note:#e supported range is from D8999298298D to D2852:8D

>TETME() *> date and time combination Fo"mat 3333QMMQ HHMMSS

Note:#e supported range is from D8999298298 99099099D to D2852:85:0F0FD

TMEST>M%() *> timestam- TMEST>M% values a"e sto"ed as te numbe" o; seconds

since te Bni= e-oc (/140Q01Q01 000000/ BTC) Fo"mat 3333QMMQ

HHMMSS

Note:#e supported range is from D8O9298298 99099098D ' to D59:P2982

9 9:0809OD '

TME() > time Fo"mat HHMMSS

Note:#e supported range is from D2P:P0F0FD to DP:P0F0FD

3E>R() > +ea" in t2oQdi#it o" ;ou"Qdi#it ;o"mat

Note:Malues allo!ed in four2digit format0 898 to 58FF. Malues allo!ed in

t!o2digit format0 O9 to T" representing years from 8O9 to 59T


79/107

>&en if +A&I& and I&SA* return t#e same format" t#ey !or3 ery differently. In

an INS&, or *+A& query" t#e I&SA* automatically set itself to t#e current date and

time. I&SA* also accepts arious formats" li3e CCCC++$$SS"CC++$$SS" CCCC++" or CC++.

SQL Ser5er Data T')es

Chara*ter strings:

Data type Description &tora(e

ca"(n) Fi=edQlen#t ca"acte" st"in# Ma=imum 000 ca"acte"s n

va"ca"(n) Aa"iableQlen#t ca"acte" st"in# Ma=imum 000 ca"acte"s

va"ca"(ma=) Aa"iableQlen#t ca"acte" st"in# Ma=imum 10$@1@

ca"acte"s

te=t Aa"iableQlen#t ca"acte" st"in# Ma=imum :! o; te=t data

Uni*ode strings:


nca"(n) Fi=edQlen#t Bnicode data Ma=imum @000 ca"acte"s

nva"ca"(n) Aa"iableQlen#t Bnicode data Ma=imum @000 ca"acte"s

nva"ca"(ma=) Aa"iableQlen#t Bnicode data Ma=imum 6$5041 ca"acte"s

nte=t Aa"iableQlen#t Bnicode data Ma=imum :! o; te=t data

Binar' t')es:


bit >llo2s 0 1 o" 'BLL

bina"+(n) Fi=edQlen#t bina"+ data Ma=imum 000 b+tes

va"bina"+(n) Aa"iableQlen#t bina"+ data Ma=imum 000 b+tes

va"bina"+(ma=) Aa"iableQlen#t bina"+ data Ma=imum :!


80/107

ima#e Aa"iableQlen#t bina"+ data Ma=imum :!

Nu$ber t')es:


tin+int >llo2s 2ole numbe"s ;"om 0 to 66 1 b+te

smallint >llo2s 2ole numbe"s bet2een Q$5 and $5 b+tes

int >llo2s 2ole numbe"s bet2een Q1@@$5@ and 1@@$5@ @ b+tes

bi#int >llo2s 2ole numbe"s bet2een Q4$$0$56@60 and

4$$0$56@60

b+tes

decimal(-s) Fi=ed -"ecision and scale numbe"s

Allo!s numbers from 289U:P V8 to 89U:P W8.

#e p parameter indicates t#e maximum total number of digits t#at

can be stored (bot# to t#e left and to t#e rig#t of t#e decimal point).p must be a alue from 8 to :P. +efault is 8P.

#e s parameter indicates t#e maximum number of digits stored to

t#e rig#t of t#e decimal point. s must be a alue from 9 to p. +efault

alue is 9

6Q1

b+tes

nume"ic(-s) Fi=ed -"ecision and scale numbe"s

Allo!s numbers from 289U:P V8 to 89U:P W8.

#e p parameter indicates t#e maximum total number of digits t#atcan be stored (bot# to t#e left and to t#e rig#t of t#e decimal point).

p must be a alue from 8 to :P. +efault is 8P.

#e s parameter indicates t#e maximum number of digits stored to

t#e rig#t of t#e decimal point. s must be a alue from 9 to p. +efaultalue is 9

6Q1b+tes

smallmone+ Moneta"+ data ;"om Q1@@$5@ to 1@@$5@ @ b+tes

mone+ Moneta"+ data ;"om Q4$$0$56@60 to

4$$0$56@60

b+tes

;loat(n) Floatin# -"ecision numbe" data ;"om Q14E $0 to 14E $0

#e n parameter indicates !#et#er t#e field s#ould #old or P

@ o"

b+tes


81/107

bytes. float(5) #olds a 2byte field and float(F:) #olds an P2bytefield. +efault alue of n is F:.

"eal Floatin# -"ecision numbe" data ;"om Q$@0E $ to $@0E $ @ b+tes

Date t')es:


datetime F"om Danua"+ 1 16$ to ecembe" $1 4444 2it an accu"ac+ o;

$$$ milliseconds

b+tes

datetime F"om Danua"+ 1 0001 to ecembe" $1 4444 2it an accu"ac+ o;

100 nanoseconds

5Q b+tes

smalldatetime F"om Danua"+ 1 1400 to Dune 5 04 2it an accu"ac+ o; 1minute

@ b+tes

date Sto"e a date onl+ F"om Danua"+ 1 0001 to ecembe" $1 4444 $ b+tes

time Sto"e a time onl+ to an accu"ac+ o; 100 nanoseconds $Q6 b+tes

datetimeo;;set Te same as datetime 2it te addition o; a time one o;;set Q10

b+tes

timestam- Sto"es a uni7ue numbe" tat #ets u-dated eve"+ time a "o2 #ets

c"eated o" modi;ied Te timestam- value is based u-on an inte"nal

cloc< and does not co""es-ond to "eal time Eac table ma+ ave

onl+ one timestam- va"iable

ther data t')es:


s7l_va"iant Sto"es u- to 000 b+tes o; data o; va"ious data t+-es e=ce-t te=t nte=t and

timestam-

uni7ueidenti;ie" Sto"es a #loball+ uni7ue identi;ie" (:B)

=ml Sto"es ML ;o"matted data Ma=imum :!

cu"so" Sto"es a "e;e"ence to a cu"so" used ;o" database o-e"ations

table Sto"es a "esultQset ;o" late" -"ocessin#


82/107

SQL ,unctions

SQL #as many built2in functions for performing calculations on data.

SQL &ggregate %un*tions

SQL aggregate functions return a single alue" calculated from alues in a column.

seful aggregate functions0

>A:() Q Retu"ns te ave"a#e value COB'T() Q Retu"ns te numbe" o; "o2s

FRST() Q Retu"ns te ;i"st value

L>ST() Q Retu"ns te last value

M>() Q Retu"ns te la"#est value

M'() Q Retu"ns te smallest value

SBM() Q Retu"ns te sum

SQL S*aar +un*tions

SQL scalar functions return a single alue" based on t#e input alue.

seful scalar functions0

BC>SE() Q Conve"ts a ;ield to u--e" case

LC>SE() Q Conve"ts a ;ield to lo2e" case

M() Q E=t"act ca"acte"s ;"om a te=t ;ield

LE'() Q Retu"ns te len#t o; a te=t ;ield

ROB'() Q Rounds a nume"ic ;ield to te numbe" o; decimals s-eci;ied

'O,() Q Retu"ns te cu""ent s+stem date and time

FORM>T() Q Fo"mats o2 a ;ield is to be dis-la+ed


83/107

Ti):#e aggregate functions and t#e scalar functions !ill be explained in details in t#e next

c#apters.

SQL A3-45 ,unction

The &;@A %un*tion

#e AMG() function returns t#e aerage alue of a numeric column.

SQL A3-45 Syntax

SELECT >A:(column_name) FROM table_name

SQL &;@A ,/a$)e

-e #ae t#e follo!ing 76rders7 table0

O_Id OrderDate OrderPrice C%stomer

1 00P11P1 1000 Hansen

00P10P$ 1500 'ilsen

$ 00P04P0 00 Hansen

@ 00P04P0$ $00 Hansen

6 00P0P$0 000 Densen

5 00P10P0@ 100 'ilsen

No! !e !ant to find t#e aerage alue of t#e 76rder*rice7 fields.


SELECT >A:(O"de"%"ice) >S O"de">ve"a#e FROM O"de"s



84/107

OrderA*era(e

460

No! !e !ant to find t#e customers t#at #ae an 6rder*rice alue #ig#er t#an t#e aerage6rder*rice alue.


SELECT Custome" FROM O"de"s

,HERE O"de"%"ice9(SELECT >A:(O"de"%"ice) FROM O"de"s)


C%stomer

Hansen

'ilsen

Densen

SQL CO%NT45 ,unction

#e '6N() function returns t#e number of ro!s t#at matc#es a specified criteria.

SQL CO%NT4column6name5 Syntax

#e '6N(column) function returns t#e number of records in a table0

SELECT COB'T(*) FROM table_name


85/107


86/107


87/107

SQL ,IRST45 Syntax

SELECT FRST(column_name) FROM table_name

SQL %#RST@A ,/a$)e



1 00P11P1 1000 Hansen

00P10P$ 1500 'ilsen

$ 00P04P0 00 Hansen

@ 00P04P0$ $00 Hansen


5 00P10P0@ 100 'ilsen

No! !e !ant to find t#e first alue of t#e 76rder*rice7 column.


SELECT FRST(O"de"%"ice) >S Fi"stO"de"%"ice FROM O"de"s

Ti):-or3around if =I,S() function is not supported0

SELECT O"de"%"ice FROM O"de"s ORER !3 O_d LMT 1


FirstOrderPrice

1000


88/107

SQL LAST45 ,unction

The L&ST@A %un*tion#e LAS() function returns t#e last alue of t#e selected column.

SQL LAST45 Syntax

SELECT L>ST(column_name) FROM table_name

SQL L&ST@A ,/a$)e



1 00P11P1 1000 Hansen

00P10P$ 1500 'ilsen

$ 00P04P0 00 Hansen

@ 00P04P0$ $00 Hansen


5 00P10P0@ 100 'ilsen

No! !e !ant to find t#e last alue of t#e 76rder*rice7 column.


SELECT L>ST(O"de"%"ice) >S LastO"de"%"ice FROM O"de"s

Ti):-or3around if LAS() function is not supported0

SELECT O"de"%"ice FROM O"de"s ORER !3 O_d ESC LMT 1



89/107

LastOrderPrice

100

SQL (A.45 ,unction

The M&@A %un*tion

#e AK() function returns t#e largest alue of t#e selected column.

SQL (A.45 Syntax

SELECT M>(column_name) FROM table_name

SQL M&@A ,/a$)e



1 00P11P1 1000 Hansen

00P10P$ 1500 'ilsen

$ 00P04P0 00 Hansen

@ 00P04P0$ $00 Hansen


5 00P10P0@ 100 'ilsen

No! !e !ant to find t#e largest alue of t#e 76rder*rice7 column.


SELECT M>(O"de"%"ice) >S La"#estO"de"%"ice FROM O"de"s


90/107


91/107

SELECT M'(O"de"%"ice) >S SmallestO"de"%"ice FROM O"de"s


&mallestOrderPrice

100

SQL S%(45 ,unction

The SUM@A %un*tion

#e S() function returns t#e total sum of a numeric column.

SQL S%(45 Syntax

SELECT SBM(column_name) FROM table_name

SQL SUM@A ,/a$)e



1 00P11P1 1000 Hansen

00P10P$ 1500 'ilsen

$ 00P04P0 00 Hansen

@ 00P04P0$ $00 Hansen


5 00P10P0@ 100 'ilsen

No! !e !ant to find t#e sum of all 76rder*rice7 fields7.


92/107


SELECT SBM(O"de"%"ice) >S O"de"Total FROM O"de"s


OrderTotal

600

SQL -RO% !" Statement

Aggregate functions often need an added G,6* 1C statement.

The ;RU! BY State$ent

#e G,6* 1C statement is used in con%unction !it# t#e aggregate functions to group t#e

result2set by one or more columns.

SQL -RO% !" Syntax

SELECT column_name a##"e#ate_;unction(column_name)FROM table_name

,HERE column_name o-e"ato" value

:ROB% !3 column_name

SQL ;RU! BY ,/a$)e



1 00P11P1 1000 Hansen

00P10P$ 1500 'ilsen

$ 00P04P0 00 Hansen


93/107

@ 00P04P0$ $00 Hansen


5 00P10P0@ 100 'ilsen

No! !e !ant to find t#e total sum (total order) of eac# customer.

-e !ill #ae to use t#e G,6* 1C statement to group t#e customers.


SELECT Custome"SBM(O"de"%"ice) FROM O"de"s

:ROB% !3 Custome"


C%stomer &!,-OrderPrice.

Hansen 000

'ilsen 100

Densen 000

Nice/ IsnDt it 0)

LetDs see !#at #appens if !e omit t#e G,6* 1C statement0




Hansen 600

'ilsen 600

Hansen 600

Hansen 600


94/107

Densen 600

'ilsen 600

#e result2set aboe is not !#at !e !anted.

,/)anation o+ 2h' the abo5e S,L,CT state$ent *annot be used:#e S&L&' statement

aboe #as t!o columns specified ('ustomer and S(6rder*rice). #e 7S(6rder*rice)7

returns a single alue (t#at is t#e total sum of t#e 76rder*rice7 column)" !#ile 7'ustomer7returns T alues (one alue for eac# ro! in t#e 76rders7 table). #is !ill t#erefore not gie us t#e

correct result. $o!eer" you #ae seen t#at t#e G,6* 1C statement soles t#is problem.

;RU! BY More Than ne Cou$n

-e can also use t#e G,6* 1C statement on more t#an one column" li3e t#is0

SELECT Custome"O"de"ateSBM(O"de"%"ice) FROM O"de"s

:ROB% !3 Custome"O"de"ate

SQL HA3IN- Clause

The 1N; Cause

#e $AMING clause !as added to SQL because t#e -$&,& 3ey!ord could not be used !it#

aggregate functions.

SQL HA3IN- Syntax

SELECT column_name a##"e#ate_;unction(column_name)

FROM table_name


:ROB% !3 column_name

H>A': a##"e#ate_;unction(column_name) o-e"ato" value

SQL 1N; ,/a$)e


95/107



1 00P11P1 1000 Hansen

00P10P$ 1500 'ilsen

$ 00P04P0 00 Hansen

@ 00P04P0$ $00 Hansen


5 00P10P0@ 100 'ilsen

No! !e !ant to find if any of t#e customers #ae a total order of less t#an 5999.



:ROB% !3 Custome"

H>A': SBM(O"de"%"ice)8000



'ilsen 100

No! !e !ant to find if t#e customers 7$ansen7 or 7Eensen7 #ae a total order of more t#an

8F99.

-e add an ordinary -$&,& clause to t#e SQL statement0


,HERE Custome"./Hansen/ OR Custome"./Densen/:ROB% !3 Custome"

H>A': SBM(O"de"%"ice)91600




96/107

Hansen 000

Densen 000

SQL %CASE45 ,unction

The UC&S,@A %un*tion

#e 'AS&() function conerts t#e alue of a field to uppercase.

SQL %CASE45 Syntax

SELECT BC>SE(column_name) FROM table_name

Syntax )or SQL Ser'er

SELECT B%%ER(column_name) FROM table_name

SQL UC&S,@A ,/a$)e






No! !e !ant to select t#e content of t#e 7LastName7 and 7=irstName7 columns aboe" and

conert t#e 7LastName7 column to uppercase.


SELECT BC>SE(Last'ame) as Last'ameFi"st'ame FROM %e"sons


97/107


LastName FirstName

H>'SE' Ola

SAE'SO' Tove

%ETTERSE' &a"i

SQL LCASE45 ,unction

The LC&S,@A %un*tion

#e L'AS&() function conerts t#e alue of a field to lo!ercase.

SQL LCASE45 Syntax

SELECT LC>SE(column_name) FROM table_name

Syntax )or SQL Ser'erSELECT LO,ER(column_name) FROM table_name

SQL LC&S,@A ,/a$)e







98/107


99/107


100/107






No! !e !ant to select t#e lengt# of t#e alues in t#e 7Address7 column aboe.


SELECT LE'(>dd"ess) as Len#tO;>dd"ess FROM %e"sons


Len(t$O"Address

1

4

4

SQL RO%ND45 ,unction

The RUND@A %un*tion

#e ,6N+() function is used to round a numeric field to t#e number of decimals specified.

SQL RO%ND45 SyntaxSELECT ROB'(column_namedecimals) FROM table_name

Parameter Description

column_name Re7ui"ed Te ;ield to "ound


101/107

decimals Re7ui"ed S-eci;ies te numbe" o; decimals to be "etu"ned

SQL RUND@A ,/a$)e

-e #ae t#e follo!ing 7*roducts7 table0

Prod_Id Prod%ctName !nit !nitPrice

1 Da"lsbe"# 1000 # 10@6

Masca"-one 1000 # $65

$ :o"#onola 1000 # 165

No! !e !ant to display t#e product name and t#e price rounded to t#e nearest integer.


SELECT %"oduct'ame ROB'(Bnit%"ice0) as Bnit%"ice FROM %"oducts


Prod%ctName !nitPrice

Da"lsbe"# 10

Masca"-one $$

:o"#onola 15

SQL NOW45 ,unction

The NW@A %un*tion

#e N6-() function returns t#e current system date and time.


102/107

SQL NOW45 Syntax

SELECT 'O,() FROM table_name

SQL NW@A ,/a$)e



1 Da"lsbe"# 1000 # 10@6

Masca"-one 1000 # $65

$ :o"#onola 1000 # 165

No! !e !ant to display t#e products and prices per todayDs date.


SELECT %"oduct'ame Bnit%"ice 'o2() as %e"ate FROM %"oducts


Prod%ctName !nitPrice PerDate

Da"lsbe"# 10@6 10PP00 1160 >M

Masca"-one $65 10PP00 1160 >M

:o"#onola 165 10PP00 1160 >M

SQL ,OR(AT45 ,unction

The %RM&T@A %un*tion

#e =6,A() function is used to format #o! a field is to be displayed.


103/107

SQL ,OR(AT45 Syntax

SELECT FORM>T(column_name;o"mat) FROM table_name

Parameter Description

column_name Re7ui"ed Te ;ield to be ;o"matted

;o"mat Re7ui"ed S-eci;ies te ;o"mat

SQL %RM&T@A ,/a$)e



1 Da"lsbe"# 1000 # 10@6

Masca"-one 1000 # $65

$ :o"#onola 1000 # 165

No! !e !ant to display t#e products and prices per todayDs date (!it# todayDs date displayed int#e follo!ing format 7CCCC22++7).


SELECT %"oduct'ame Bnit%"ice FORM>T('o2()/3333QMMQ/) as %e"ate

FROM %"oducts


Prod%ctName !nitPrice PerDate

Da"lsbe"# 10@6 00Q10Q0

Masca"-one $65 00Q10Q0

:o"#onola 165 00Q10Q0


104/107

SQL Quic8 Re)erence ,rom W9Sc:ools

&/L &tatement &ynta0

>' P OR SELECT column_name(s)

FROM table_name

,HERE condition

>'?OR condition

>LTER T>!LE >LTER T>!LE table_name

> column_name datat+-e

or

AL&, A1L& table' value

CRE>TE >T>!>SE CRE>TE >T>!>SE database_name

CRE>TE T>!LE CRE>TE T>!LE table_name

(

column_name1 data_t+-e

column_name data_t+-e

column_name data_t+-e

)

CRE>TE 'E CRE>TE 'E inde=_name


or


105/107


106/107


or

INS&, IN6 table


107/107

FROM old_table_name

or

S&L&' columnLL SELECT column_name(s) FROM table_name1B'O' >LL

SELECT column_name(s) FROM table_name

B%>TE B%>TE table_name

SET column1.value column.value

,HERE some_column.some_value

,HERE SELECT column_name(s)

FROM table_name


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