Post on 09-Jan-2016
description
Chapter NineData Manipulation Language (DML)
Functions
Objectives• Single Row functions
• Character functions
• Number functions
• Date functions
2
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
4
Single Row Functions
• Character
• Number
• Date
• Conversion
• General
5
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;