sql overview , oracle data type , ddl and constraints · (ddl) load data (dml) tables in the...

LECTURE9-PART2:

DATA MANIPULATION IN SQL , ADVANCED

SQL QUERIES AND VIEW

11

Ref. Chapter5 and 6

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I S220 / IS 422 : Dat abase Fundam ent a l s

from

“Database Systems: A Practical Approach to Design, Implementation and Management.”

Thomas Connolly, Carolyn Begg.

The Process of Database Design22

Conceptual Design (ERD)

Logical Design

(Relational Model)

Physical Design

Create schema

(DDL)

Load Data

(DML)

Tables in the Examples

Customer(custNo, custName, custSt, custCity, age)

Product(prodNo, prodName, prodDes, price)

Orders(ordNo, ordDate, custNo, prodNo, quantity)

Where

custName, custSt, custCity, prodName, prodDes are strings

ordDate is date

Others are numbers

Lecture9

33

Sample Data in Customer Table

Lecture9

44

custNo custName custSt custCity age

1 C1 Olaya St Jeddah 20

2 C2 Mains St Riyadh 30

3 C3 Mains Rd Riyadh 25

4 C4 Mains Rd Dammam

5 C5 Mains Rd Riyadh

Sample Data in Product Table

Lecture9

55

prodNo prodName prodDes price

100 P0 Food 100

101 P1 healthy food 100

102 P2 200

103 P3 self_raising

flour,80%wheat

300

104 P4 network 80x 300

Sample Data in Orders Table

Lecture9

66

ordNo ordDate custNo prodNo quantity

1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

Aggregate Functions

COUNT - returns the number of selected values

SUM - returns the sum of selected (numeric) values

AVG - returns the average of selected (numeric)

values

MIN - returns the minimum of selected values

MAX - returns the maximum of selected values

Lecture9

77

Use of COUNT(column_name)

The COUNT(column_name) function returns the

number of values (NULL values will not be

counted) of the specified column

Syntax

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88

SELECT COUNT(column_name)

FROM table_name;

SELECT COUNT(column_name)

FROM table_name;

Use of COUNT(column_name)

Example 1: List the number of products in the product table

SELECT count(prodNo) FROM product;

Example 2: List the number of product descriptions in the product table

SELECT count(prodDes) FROM product;

Note: count(prodDes) does not count rows that have NULL value for prodDes.

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99

COUNT(PRODNO)

-------------------------

5

COUNT(PRODDES)

------------------------

4

Use of COUNT(*)

The COUNT(*) function returns the number of

records in a table (NULL values will be counted)

Syntax

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1010

SELECT COUNT(*)

FROM table_name;

SELECT COUNT(*)

FROM table_name;

Use of COUNT (*)

Example 1: How many products are there in the product table?

SELECT count(*) FROM product;

Example 2: How many products are priced at 300?

SELECT count(*)

FROM product

WHERE price =300;

Note: count(*) also count rows that have NULL values

Lecture9

1111

prod

No

prodNam

e

prodDes price

100 P0 Food 100


102 P2 200

103 P3 self_raising

flour,80%wh

eat

300


COUNT(*)

-------------------------

5

COUNT(*)

---------------

2

Use of COUNT(DISTINCT column_name)

The COUNT(DISTINCT column_name) function

returns the number of distinct values of the

specified column:

Syntax

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SELECT COUNT(DISTINCT column_name)

FROM table_name;

SELECT COUNT(DISTINCT column_name)

FROM table_name;

Use of COUNT(DISTINCT column_name)

Example1: How many cities are the customers

located in ?

SELECT count(distinct custCity) from customer;

Example 2: How many customers ordered products

since 01/01/2003?

SELECT count(distinct custNo)

FROM orders

WHERE ordDate >= '01-jan-2003';

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ordNo ordDate cust

No

prodNo quantit

y

1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

COUNT(DISTINCT CUSTCITY)

-----------------------------------------

3

COUNT(DISTINCT CUSTNO)

------------------------------------

3

custNo custNam

e

custSt custCity age

1 C1 Olaya St Jeddah 20

2 C2 Mains St Riyadh 30

3 C3 Mains Rd Riyadh 25

4 C4 Mains Rd Dammam

5 C5 Mains Rd Riyadh

Use of SUM

The SUM() function returns the total sum of a

numeric column.

The MIN() function returns the smallest value of

the selected column.

The MAX() function returns the largest value of

the selected column.

The AVG() function returns the average value of

a numeric column.

Syntax

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SELECT

SUM(column_name),MIN(column_name),MAX(column_name),AVG(column_name)

FROM table_name;

SELECT

SUM(column_name),MIN(column_name),MAX(column_name),AVG(column_name)

FROM table_name;

Use of SUM Example

Example 1: How many products pieces were ordered by customer 1?

SELECT SUM(quantity)

FROM orders

WHERE custNo =1;

Example 2: How many orders were made by customer 1 and how many products pieces did he order?

SELECT count(ordNo), SUM(quantity)

FROM orders

WHERE custNo =1; Lecture9

1515

ordNo ordDate cust

No

prodNo quantit

y

1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

SUM(QUANTITY)

-----------------------

4

COUNT(ORDNO) SUM(QUANTITY)

--------------------- ----------------------

3 4

Example Use of AVG, MIN and MAX

Example: list the minimum, maximum and average price

of all products.

SELECT MIN(price), MAX(price), AVG(price)

FROM product;

Note: if some product's price are NULLs, then SUM and

AVG do not take those products into consideration. Lecture9

1616

prodNo prodNam

e

prodDes price

100 P0 Food 100


102 P2 200

103 P3 self_raising

flour,80%wh

eat

300


MIN(PRICE) MAX(PRICE) AVG(PRICE)

---------------- ---------------- ----------------

100 300 200

Lecture91717

Advanced queries (GROUP BY)

General Syntax of SELECT command

SELECT [DISTINCT]

{* | [columnExpression, ……. }

FROM TableName

[WHERE condition]

[GROUP BY columnList]

[HAVING condition]

[ORDER BYcolumnList]

Order of the clauses cannot be changed.

Only SELECT and FROM are mandatory

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The GROUP BY Statement

The GROUP BY statement is used in conjunction with

the aggregate functions to group the result-set by

one or more columns.

Syntax

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SELECT column_name, aggregate_function(column_name)

FROM table_name

WHERE condition

GROUP BY column_name;


FROM table_name

WHERE condition

GROUP BY column_name;

Use of GROUP BY

Use GROUP BY clause to get sub-totals.

SELECT and GROUP BY closely integrated: each

item in SELECT list must be single-valued per group,

and SELECT clause may only contain:

Column names in the group by clause

Aggregate functions

Constants

Expression involving combinations of the above

If WHERE is used with GROUP BY, WHERE is

applied first, then groups are formed from rows

satisfying condition.Lecture9

2020

Example 1 ( use of group by )

Orders

find the total (total order) of each customer.

use the GROUP BY statement to group the

customers.SELECT Customer, SUM(OrderPrice)

FROM Orders

GROUP BY Customer;Lecture9

2121

O_Id OrderDate OrderPrice Customer

1 2008/11/12 1000 Nora

2 2008/10/23 1600 Sara

3 2008/09/02 700 Nora

4 2008/09/03 300 Nora

5 2008/08/30 2000 Yara

6 2008/10/04 100 Sara

Nora

Sara

Yara

Example 1

The result ( output ):

what happens if we omit the GROUP BY statement

SELECT Customer,SUM(OrderPrice) FROM

Orders;

The result

Lecture9

2222

Customer SUM(OrderPrice)

Nora 2000

Sara 1700

Yara 2000

Customer SUM(OrderPrice)

Nora 5700

Sara 5700

Nora 5700

Nora 5700

Yara 5700

Sara 5700

Example 2

List the quantity of each product ordered during

Jan 2003.

SELECT prodNo, sum(quantity)

FROM orders

WHERE ordDate>='01-jan-2003' AND

ordDate<'01-Feb-2003'

GROUP BY prodNo;

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1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

PRODNO SUM(QUANTITY)

-------------- --------------------

100 4

102 1

101 2

Example 3

return the minimum and maximum salaries for each

department in the employees table

SELECT deptNumber, MIN(salary), MAX (salary)

FROM employees

GROUP BY deptNumber

ORDER BY deptNumber;

Lecture9

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Employee No. First Name Last Name Dept Number Salary

E1 Mandy Smith D1 50000

E2 Daniel Hodges D2 45000

E3 Shaskia Ramanthan D2 58000

E4 Graham Burke D1 44000

E5 Annie Nguyen D1 60000D1

D2

DEPTNUMBER MIN(SALARY) MAX(SALARY)

--------------------- ------------------ -------------------

D1 44000 60000

D2 45000 58000

SELECT count(*)

FROM EMPLOYEE;

Example 1 : no grouping






E5 Annie Nguyen D1 60000

Without group by COUNT(*) returns the number of rows in the table

COUNT(*)

-------------

5

Example 4Grouping Output from Queries

Lecture9

2525

DEPTNUMBER COUNT(*)

---------------- -------------

D1 3

D2 2







Example 2 : group by

SELECT deptNumber, count(*)

FROM EMPLOYEE

GROUP BY deptNumber


Grouping Output from Queries

Lecture9

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Use of HAVING

HAVING clause is designed for use with GROUP BY to restrict

groups that appear in final result table.

Similar to WHERE, but WHERE filters individual rows whereas

HAVING filters groups.

Column names in HAVING clause must also appear in the

GROUP BY list or be contained within an aggregate function.

SYNTAX

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2727


FROM table_name

WHERE column_name operator value

GROUP BY column_name

HAVING aggregate_function(column_name) operator value

;


FROM table_name

WHERE column_name operator value

GROUP BY column_name

HAVING aggregate_function(column_name) operator value

;

EXAMPLE 1

find if any of the customers have a total order of less

than 2000

SELECT Customer,SUM(OrderPrice)

FROM Orders

GROUP BY Customer

HAVING SUM(OrderPrice)<2000;

- Without Having

Lecture9

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1 2008/11/12 1000 Nora

2 2008/10/23 1600 Sara

3 2008/09/02 700 Nora

4 2008/09/03 300 Nora

5 2008/08/30 2000 Yara

6 2008/10/04 100 Sara

CUSTOMER SUM(ORDERPRICE)

----------------- -------------------------

SARA 1700CUSTOMER SUM(ORDERPRICE)

----------------- -------------------------

NORA 2000

SARA 1700

YARA 2000

Example 2

find if the customers “Nora" or “Yara" have a total

order of more than 1500

SELECT Customer,SUM(OrderPrice)

FROM Orders

WHERE Customer=‘Nora' OR Customer=‘Yara'

GROUP BY Customer

HAVING SUM(OrderPrice)>1500 ;

Lecture9

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1 2008/11/12 1000 Nora

2 2008/10/23 1600 Sara

3 2008/09/02 700 Nora

4 2008/09/03 300 Nora

5 2008/08/30 2000 Yara

6 2008/10/04 100 Sara

CUSTOMER SUM(ORDERPRICE)

----------------- -------------------------

NORA 2000

YARA 2000

Example 3

List the product number and the quantity ordered for each

product which has a total quantity of more than 2 during Jan

2003.

SELECT prodNo, sum(quantity)

FROM orders

WHERE ordDate>='01-jan-2003' AND ordDate<'01-Feb-2003'

GROUP BY prodNo

HAVING sum(quantity)>2;

Lecture9

3030


1 01-jan-2003 1 100 2

2 02-jan-2003 1 101 1

3 01-jan-2003 2 102 1

4 01-jan-2003 3 100 2

5 03-jan-2003 1 101 1

6 06-mar-2003 2 100 10

100= 4

101=2

102 = 1

PRODNO SUM(QUANTITY)

------------- ----------------------

100 4

Example 4

List the department number and the total number of employee in that

department for each department that has more than two employees

SELECT deptNumber, count(*)

FROM EMPLOYEE

GROUP BY deptNumber

HAVING count(*)>2


Lect

ure9

3131DEPTNUMBER COUNT(*)

---------------- --------------

D1 3

DEPTNUMBER COUNT(*)

---------------- -------------

D1 3

D2 2







Lecture9

3232

Lecture93333

Views

Dynamic result of one or more relational operations operating on base relations to produce another relation.

Virtual relation that does not necessarily actually exist in the database but is produced upon request, at time of request.

Contents of a view are defined as a query on one or more base relations.

With view resolution, any operations on view are automatically translated into operations on relations from which it is derived.

With view materialization, the view is stored as a temporary table,

which is maintained as the underlying base tables are updated.

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Pearson Education © 2009

SQL - CREATE VIEW

Syntax:

Can assign a name to each column in view.

If list of column names is specified, it must have same number of items as number of columns produced by subselect.

If omitted, each column takes name of corresponding column in subselect.

List must be specified if there is any ambiguity in a column name.

The subselect is known as the defining query.

WITH CHECK OPTION ensures that if a row fails to satisfy WHERE clause of defining query, it is not added to underlying base table.

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CREATE VIEW ViewName [ (newColumnName [,...]) ]AS subselect

[WITH [CASCADED | LOCAL] CHECK OPTION]

CREATE VIEW ViewName [ (newColumnName [,...]) ]AS subselect

[WITH [CASCADED | LOCAL] CHECK OPTION]

Example 7.3 - Create Horizontal View

Create view so that manager at branch B003 can only see

details for staff who work in his or her office.

CREATE VIEW Manager3Staff

AS SELECT *

FROM Staff

WHERE branchNo = ‘B003’;

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Example 7.4 - Create Vertical View

Create view of staff details at branch B003 excluding salaries.

CREATE VIEW Staff3

AS SELECT staffNo, fName, lName, position, sex

FROM Staff


3737


SQL - DROP VIEW

Syntax:

With CASCADE, all related dependent objects are deleted; i.e. any views defined on view being dropped.

With RESTRICT (default), if any other objects depend for their existence on continued existence of view being dropped, command is rejected.

For example:

DROP VIEW Manager3Staff;

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DROP VIEW ViewName [RESTRICT | CASCADE]DROP VIEW ViewName [RESTRICT | CASCADE]

View Updatability

All updates to base table reflected in all views that

encompass base table.

Similarly, may expect that if view is updated then

base table(s) will reflect change.

3939


View Updatability

ISO specifies that a view is updatable if and only if:

- DISTINCT is not specified.

- Every element in SELECT list of defining query is acolumn name and no column appears more thanonce.

- FROM clause specifies only one table, excludingany views based on a join, union, intersection ordifference.

- No nested SELECT referencing outer table.

- No GROUP BY or HAVING clause.

- Also, every row added through view must notviolate integrity constraints of base table.

4040


WITH CHECK OPTION

Rows exist in a view because they satisfy WHEREcondition of defining query.

If a row changes and no longer satisfies condition, itdisappears from the view.

New rows appear within view when insert/updateon view cause them to satisfy WHERE condition.

Rows that enter or leave a view are calledmigrating rows.

WITH CHECK OPTION prohibits a row migrating out of the view.

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WITH CHECK OPTION

LOCAL/CASCADED apply to view hierarchies.

With LOCAL, any row insert/update on view and any view directly or indirectly defined on this view must not cause row to disappear from view unless row also disappears from derived view/table.

With CASCADED (default), any row insert/ update on this view and on any view directly or indirectly defined on this view must not cause row to disappear from the view.

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Example 7.6 - WITH CHECK OPTION

CREATE VIEW Manager3Staff

AS SELECT *

FROM Staff

WHERE branchNo = ‘B003’

WITH CHECK OPTION;

Cannot update branch number of row B003 to B002as this would cause row to migrate from view.

Also cannot insert a row into view with a branchnumber that does not equal B003.

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Now consider the following:

CREATE VIEW LowSalaryAS SELECT * FROM Staff WHERE salary > 9000;

CREATE VIEW HighSalaryAS SELECT * FROM LowSalary

WHERE salary > 10000

WITH LOCAL CHECK OPTION;

CREATE VIEW Manager3StaffAS SELECT * FROM HighSalary


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UPDATE Manager3Staff

SET salary = 9500

WHERE staffNo = ‘SG37’;

This update would fail: although update would cause row todisappear from HighSalary, row would not disappear fromLowSalary.

However, if update tried to set salary to 8000, update wouldsucceed as row would no longer be part of LowSalary.

If HighSalary had specified WITH CASCADED CHECK OPTION,setting salary to 9500 or 8000 would be rejected because rowwould disappear from HighSalary.

To prevent anomalies like this, each view should be created usingWITH CASCADED CHECK OPTION.

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sql overview , oracle data type , ddl and constraints · (ddl) load data (dml) tables in the...

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