Chapter NineData Manipulation Language (DML)

Functions

Objectives• Single Row functions

• Character functions

• Number functions

• Date functions

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Functions

• Introduction

• Types of functions– Single row– Multiple rows

Single Row Functions:

•FACTS:– Act on each row

– Return one result per row

– May modify the data type

– Can be nested

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Single Row Functions

• Character

• Number

• Date

• Conversion

• General

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Character Manipulation:

• LOWER(Col | Exp)LOWER(‘Database course’)

• UPPER (Col | Exp)UPPER (‘Database course’)

• INITCAP (Col | Exp)

INITCAP (‘Database course’)

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Character Manipulation

• CONCAT (Col1 | Exp1, Col2 | Exp2)CONCAT(‘This ‘,’that’)

• SUBSTR(Col | Exp,n[,m])SUBSTR(‘This is it’,2,5)

• LPAD(Col | Exp,n,’string’)LPAD(name,9,’.’)

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Character Manipulation

• LENGTH(Col | Exp)LENGTH(‘this is it’)

• CHR(integer)CHR(97)

• INSTR(‘Computer’,’m’)

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List(Characters):

• Example:

• SELECT LOWER(name), UPPER(major), LENGTH(name)

FROM student;

• SELECT CONCAT(Name , Address) , GPAFROM Student;

 • SELECT Name || ‘--->‘ || Address , GPA

FROM Student;

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List(Characters):

• SELECT RPAD (Name, 40, ‘.’), GPA

FROM Student;

JOHN............... 3.1

MARY ............. 3.2

• SELECT RPAD (Name, 20), GPA

FROM Student;

MARY 3.2

MOHAMMAD 3.3

• SELECT LPAD (Name, 20), GPA

FROM Student;

MARY 3.2

MOHAMMAD 3.3

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List(Characters):

• RTRIM(Col)

RTRIM (Name)

RTRIM (Name, ‘.’)

LTRIM (Name, ‘ABC’)

 

LTRIM ( RTRIM( Name, ‘.’ ), ‘A’)

From Student;

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List(Characters):

• SELECT NameFROM StudentWHERE LENGTH(Address)<20;

• SELECT Name, SUBSTR (SSN, 5 ,2)

FROM Student;

• SELECT Name, SUBSTR (SSN,5)FROM Student;

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List(Characters):

• SELECT RPAD (INITCAP(LOWER(Name)),70,’.’),

SUBSTR (SSN,5)

FROM Student;

• SELECT NameFROM StudentWHERE SUBSTR (SSN,5,2)=’80’;

• SELECT Name, SUBSTR (SSN,-4)FROM Student;

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List(Characters):

• SELECT Name, INSTR (Name,’R’)FROM Student;

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

MARY 3JOHN 0ROBIN 1

• SELECT Name, INSTR (Name,’R’,1,2)FROM Student;

• SELECT Name, INSTR(Address,’FROSTBURG’)FROM Student;

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List(Characters):

Character Manipulations

• REPLACE(string, searchSt [,replace])REPLACE(address,’21532’, ‘21211’)

• TRANSLATE (string, fromSt, toSt)TRANSLATE(‘12345678’, ‘123’, ‘999’)

• ASCII(string)ASCII(‘A’)

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List(Characters):

Character Manipulations

• SOUNDEX

SELECT name, GPA

FROM student

WHERE

SOUNDEX (name)=SOUNDEX(‘LAVALE’);

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Character Manipulation

New Functions:

REGEXP_SUBSTR

REGEXP_INSTR

REGEXP_LIKE

REGEXP_REPLACE

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LIST(Numbers)

• ROUND (value, precision)ROUND(234.1161,2)

• TRUNC(value, precision)TRUNC(234.1161,2)

• POWER(value,exponent)POWER(3,2) 

• MOD(value1, value2)MOD(900,400)

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LIST(Numbers)

• SELECT ROUND(Salary,1)

FROM Faculty;

• SELECT TRUNC(234.111,2),

FROM DUAL;

TRUNC(234.567);

TRUNC(234.5678,-2);

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DATE:

• Date is stored in an internal numeric format: century, year, month, day, hours, minutes, second

• Default date is ‘DD-MON-YY’

• SYSDATE• CURRENT_DATE• STSTIMESTAMP

25-OCT-04 04.15.31.652000 PM

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DATE:

• Example:

List the ages of students

 

• SELECT name, SYSDATE - B_Date

FROM student;

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Date

• Date + number

• Date – number

• Date – date

• Date + number/24

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DATE:

• MONTHS_BETWEEN(day1,day2)

• SELECT name, MONTHS_BETWEEN(SYSDATE , B_Date)

age_in_month

FROM Student;

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DATE:

• ADD_MONTHS (date,n)SELECT name, ADD_MONTHS(B_Date,5) age

FROM Student;

SELECT name, ADD_MONTHS(B_Date,-15) age

FROM Student;

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DATE:

• ROUND(date [,fmt])

 • SELECT name,

ROUND (B_Date,’MONTH’)

FROM Student;

• SELECT name, ROUND(B_Date,’YEAR’)

FROM Student;

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DATE:

• ROUND(date [,fmt])

 • SELECT ’25-OCT-04’ - ROUND

(SYSDATE)

FROM DOAL;

• SELECT name, ROUND(B_Date,’YEAR’)

FROM Student;

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DATE:

• NEXT_DAY

• SELECT cycledate FROM paydate;

• SELECT NEXT_DAY(cycledate, ‘FRIDAY’)

FROM paydate;

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DATE:

LAST_DAY (date)

SELECT LAST_DAY (SYSDATE) “Last”,

SYSDATE, LAST_DAY (SYSDATE) – SYSDATE “Left”

FROM DUAL;

Last SYSDATE Left

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

31-MAY-05 28-MAY-05 4

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Conversion Function:

Implicit conversion (Automatic):

– CHAR or VARCHAR2 to NUMBER– CHAR or VARCHAR2 to DATE– NUMBER to VARCHAR2– DATE to VARCHAR2

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Conversion Function:

Explicit datatype conversion:

– TO_CHAR (NUMBER [,‘fmt’] )– TO_CHAR (DATE [,‘fmt’] )– TO_DATE (CHAR [,‘fmt’] )– TO_NUMBER (CHAR [,‘fmt’] )

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Conversion Function:

SELECT TO_CHAR(b_date,’MM/YY’)FROM student;

Format:• YYYY• YYY• YY• RR• YEAR• MM• MONTH• DD• DY• DAY• HH HH12 HH24• MI• SS

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Conversion Function:

EXTRACT (YEAR FROM B_Date)YEARMONTHDAYHOURMINUTESECOND

SELECT EXTRACT (YEAR FROM DATE ‘1999-01-08’)FROM DUAL; --1999

SELECT EXTRACT (YEAR FROM TO_DATE (B_Date, ‘DD-

MON-YY’)FROM Student;

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Conversion Function:

• SELECTSUBSTR(TO_CHAR(111223333),1,3)

||‘-’ ||

SUBSTR (TO_CHAR(111223333),4,2) || ‘-’ ||

SUBSTR(TO_CHAR(111223333),6)

FROM Student;

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Conversion Function:

• SELECT SUBSTR(ssn,1,3)

|| ‘-’ ||

SUBSTR(ssn,4,2)

|| ‘-’ ||

SUBSTR(ssn,6)

FROM Student;

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CAST

• CAST (expression) AS (Type);

CHAR NUMBER DATE ROW ROWIDVARCHAR2 TIMESTAMP

1 X X X X X

2 X X

3 X X

4 X X

5 X X

CAST (B_Date AS CHAR);

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NULLIF

NULLIF (Exp1, Exp2)IF Exp1 = Exp2 THEN RETURN

NULL ELSE RETURN

Exp1SELECT Name, NULLIF (a.major, b.major)

“oldMajor”FROM Student a, StudentHistory bWHERE a.ID = b.ID;

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NVL

NVL (Exp1,Exp2)

SELECT Name, NVL

(TO_CHAR (Commission_pct, ‘Not Applicable’))

commissionFROM Sales;

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NVL2

NVL2 (Exp1, Exp2, Exp3)

SELECT Name,

NVL2 (Commission_pct, Salary + Salary * Commission_pct, Salary)

FROM Employee;

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COALESCE

• COALESCE (exp_List)

Return the first non_null expression in the expression list:

COALESCE (Email, Address, Phone_#, Phone_W)

SELECT Product_ID, Product_Name, List_Price, Min_Price, COALESCE (List_Price, Min_Price, 10) ”Sale Price”

FROM Product;

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Use of DECODE:

• DECODE: DECODE (col/exp, compare1, result1

[,compare2, result2, …] [,default] )

SELECT name, salary, DECODE (Dept, ‘COSC’, salary*2.2,

‘MATH’, salary*1.2, ‘ART’, salary*0.2, salary)

FROM Faculty;