SQL Server Functions

This article is to put all mostly used function related in SQL Server 2005/2008

DateTime Function in SQL Server

Below are the most commonly used DateTime function in SQL Server.

• GETDATE()
• DATEADD()
• DATEPART()
• DATEDIFF()
• DATENAME()
• DAY()
• MONTH()
• YEAR()

GETDATE()

GETDATE() is very common used method which returns exact date time from the system. It does not accept any parameter. Just call it like simple function.
Example :

Declare @Date datetime 

set @Date = (SELECT GETDATE());

Print @Date 

OutPut:

Aug 15 2009  9:04PM 

DATEADD()

DATEADD() is used to add or subtract datetime. Its return a new datetime based on the added or subtracted interval.
General Syntax

 DATEADD(datepart, number, date)

datepart is the parameter that specifies on which part of the date to return a new value. Number parameter is used to increment datepart.
Example :

Declare @Date datetime 

set @Date = (SELECT GETDATE());

print  @Date -- Print Current Date

-- Adding 5 days with Current Date

SELECT DATEADD(day, 5,@Date ) AS NewTime

Output :

Aug 15 2009  9:19PM

NewTime

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

2009-08-20 21:19:15.170

DATEPART()

DATEPART() is used when we need a part of date or time from a datetime variable. We can use DATEPART() method only with select command.
Syntax

DATEPART(datepart, date)

Example :

-- Get Only Year

SELECT DATEPART(year, GETDATE()) AS 'Year'

-- Get Only Month

SELECT DATEPART(month, GETDATE()) AS 'Month'

-- Get Only hour

SELECT DATEPART(hour, GETDATE()) AS 'Hour

Output :

Year

-----------

2009

Month

-----------

8

Hour

-----------

21

DATEDIFF()

DATEDIFF() is very common function to find out the difference between two DateTime elements.
Syntax

DATEDIFF(datepart, startdate, enddate)

Example :

-- Declare Two DateTime Variable

Declare @Date1 datetime 

Declare @Date2 datetime 

-- Set @Date1 with Current Date

set @Date1 = (SELECT GETDATE());

-- Set @Date2 with 5 days more than @Date1

set @Date2 = (SELECT DATEADD(day, 5,@Date1 ))

-- Get The Date Difference

SELECT DATEDIFF(day, @Date1, @Date2) AS DifferenceOfDay

Output :

DifferenceOfDay

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

5 

DATENAME()

DATENAME() is very common and most useful function to find out the date name from the datetime value.
Example

-- Get Today 

SELECT DATENAME(dw, getdate()) AS 'Today Is'

-- Get Mont name

SELECT DATENAME(month, getdate()) AS 'Month'

Output :

Today Is

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

Saturday

Month

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

August

DAY()

DAY() is used to get the day from any date time object.
Example:

SELECT DAY(getdate()) AS 'DAY'

Output :

DAY

-----------

15

MONTH()

SELECT MONTH(getdate()) AS 'Month'

Output :

Month

-----------

8

YEAR()

SELECT YEAR(getdate()) AS 'Year'

Output :

Year

-----------

2009

String Functions

Some of the String Functions comes very handy at times. Let us discuss them one by one.

ASCII()

Returns the ASCII code value of the leftmost character of a character expression.

Syntax

ASCII ( character_expression ) 

Arguments: character_expression : Is an expression of the type char or varchar.

Return Types: Int 

Example:  

SELECT ASCII('A')  

SET TEXTSIZE 0

SET NOCOUNT ON

-- Create the variables for the current character string position 

-- and for the character string.

DECLARE @position int, @string char(15)

-- Initialize the variables.

SET @position = 1

SET @string = 'The codeProject'

WHILE @position <= DATALENGTH(@string)

   BEGIN

   SELECT ASCII(SUBSTRING(@string, @position, 1)),

      CHAR(ASCII(SUBSTRING(@string, @position, 1)))

    SET @position = @position + 1

   END

SET NOCOUNT OFF

Output:

-----------

65

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

84          T

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

104         h

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

101         e

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

and so on..... 

CHAR()  

Converts an int ASCII code to a character.  

Syntax  

CHAR ( integer_expression ) 

Arguments: integer_expression: Is an integer from 0 through 255. NULL is returned if the integer expression is not in this range.
Return Types:  character 
Example:  

SET TEXTSIZE 0

SET NOCOUNT ON

DECLARE @intCounter int

SET @intCounter = 0

WHILE (@intCounter<= 255)

               BEGIN

                               SELECT 'CHAR - ' + CHAR(@intCounter) + '. ASCII - ' + CONVERT(VARCHAR,@intCounter) 

                               SET @intCounter = @intCounter + 1

               END

SET NOCOUNT OFF

Output:

CHAR - !. ASCII - 33

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

CHAR - ". ASCII - 34

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

CHAR - #. ASCII - 35

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

CHAR - $. ASCII - 36

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

CHAR - %. ASCII - 37

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

CHAR - &. ASCII - 38

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

CHAR - '. ASCII - 39

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

CHAR - (. ASCII - 40

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

and so on.....   

NCHAR() 

Return a unicode character representing a number passed as a parameter.

Syntax 

NCHAR ( integer_expression )  

Return Types:  character 



Example : 

SELECT NCHAR(97) 

OutPut

This will return the leter "a"

DIFFERENCE()

Returns an integer value that indicates the difference between the SOUNDEX values of two character expressions.

Syntax

DIFFERENCE ( character_expression , character_expression )

Arguments:character_expression: Is an expression of type char or varchar. character_expression can also be of type text; however, only the first 8,000 bytes are significant.
Return Types:  Int
Example :

USE AdventureWorks;

GO

-- Returns a DIFFERENCE value of 4, the least possible difference.

SELECT SOUNDEX('Green'), SOUNDEX('Greene'), DIFFERENCE('Green','Greene');

GO

-- Returns a DIFFERENCE value of 0, the highest possible difference.

SELECT SOUNDEX('Blotchet-Halls'), SOUNDEX('Greene'), DIFFERENCE('Blotchet-Halls', 'Greene');

GO

Output:

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

G650  G650  4           

(1 row(s) affected)

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

B432  G650  0           

(1 row(s) affected)

LEFT() 

Returns the left most characters of a string.

Syntax

LEFT(string, length) 

string
Specifies the string from which to obtain the left-most characters.

length
Specifies the number of characters to obtain.
Example :

SELECT LEFT('Marufuzzaman',5)  

OutPut

Maruf

RIGHT()

Returns the right most characters of a string.

Syntax  

RIGHT(string, length) 

string
Specifies the string from which to obtain the left-most characters.

length
Specifies the number of characters to obtain.
Example :

SELECT RIGHT('Md. Marufuzzaman',12)  

OutPut

Marufuzzaman 

LTRIM() 

Returns a character expression after it removes leading blanks.
Example :

SELECT LTRIM('   Md. Marufuzzaman') 

OutPut

Md. Marufuzzaman

RTRIM()

Returns a character string after truncating all trailing blanks. 
Example : 

SELECT RTRIM('Md. Marufuzzaman    ') 

OutPut

Md. Marufuzzaman

REPLACE() 

Returns a string with all the instances of a substring replaced by another substring.

Syntax

REPLACE(find, replace, string)

Find
Specifies the string that contains the substring to replace all instances of with another.

Replace
Specifies the substring to locate.

String
Specifies the substring with which to replace the located substring.

Example :

SELECT REPLACE('The codeProject is ?.','?', 'your development resource')

OutPut:

 The codeProject is your development resource.

QUOTNAME()

Returns a Unicode string with the delimiters added to make the input string a valid Microsoft SQL Server delimited identifier.

Syntax

QUOTENAME ( 'character_string' [ , 'quote_character' ] )  

Arguments
' character_string '
Is a string of Unicode character data. character_string is sysname and is limited to 128 characters. Inputs greater than 128 characters return NULL.

' quote_character '
Is a one-character string to use as the delimiter. Can be a single quotation mark ( ' ), a left or right bracket ( [ ] ), or a double quotation mark ( " ). If quote_character is not specified, brackets are used.

Return Types: nvarchar(258)

Examples :
The following example takes the character string abc[]def and uses the [ and ] characters to create a valid SQL Server delimited identifier.

SELECT QUOTENAME('abc[]def')

OutPut:

[abc[]]def] 

REVERSE()

Returns a character expression in reverse order. 
Example :

SELECT REVERSE('namazzufuraM .dM')

Output: 

 Md. Marufuzzaman 

CHARINDEX

CharIndex returns the first occurance of a string or characters within another string. The Format of CharIndex is given Below:
CHARINDEX ( expression1 , expression2 [ , start_location ] )
Here expression1 is the string of characters to be found within expression2. So if you want to search ij within the word Abhijit, we will use ij as expression1 and Abhijit as expression2. start_location is an optional integer argument which identifies the position from where the string will be searched. Now let us look into some examples :

SELECT CHARINDEX('SQL', 'Microsoft SQL Server') 

OUTPUT:

11

So it will start from 1 and go on searching until it finds the total string element searched, and returns its first position. The Result will be 0 if the searched string is not found.

We can also mention the Start_Location of the string to be searched.

EXAMPLE:

SELECT CHARINDEX('SQL', 'Microsoft SQL server has a great SQL Engine',12)

So in the above example we can have the Output as 34 as we specified the StartLocation as 12, which is greater than initial SQL position(11).

PATINDEX

As a contrast PatIndex is used to search a pattern within an expression. The Difference between CharIndex and PatIndex is the later allows WildCard Characters.
PATINDEX ( '%pattern%' , expression)
Here the first argument takes a pattern with wildcard characters like '%' (meaning any string) or '_' (meaning any character).

For Example
PATINDEX('%BC%','ABCD')

Output:  

2

Another flexibility of PATINDEX is that you can specify a number of characters allowed within the Pattern. Say you want to find all of the records that contain the words "Bread", or "bread" in a string, You can use the following :

SELECT PATINDEX('%[b,B]read%', 'Tommy loves Bread') 

In this example, we mentioned both b and B in square brackets. The Result will be 13 which is same if we have searched in 'Tommy loves bread'.

LEN

Len is a function which returns the length of a string. This is the most common and simplest function that everyone use. Len Function excludes trailing blank spaces.

SELECT LEN('ABHISHEK IS WRITING THIS')

This will output 24, it is same when we write LEN('ABHISHEK IS WRITING THIS ') as LEN doesnt take trailing spaces in count.

STUFF

Stuff is another TSql Function which is used to delete a specified length of characters within a string and replace with another set of characters. The general syntax of STUFF is as below :

STUFF(character_expression1, start, length, character_expression2)Character_Expression1 represents the string in which the stuff is to be applied. start indicates the starting position of the character in character_expression1, length is the length of characters which need to be replaced. character_expression2 is the string that will be replaced to the start position.

Let us take an example :

SELECT STUFF('SQL SERVER is USEFUL',5,6,'DATABASE')

So the result will be :

SQL DATABASE is USEFUL

SUBSTRING

Substring returns the part of the string from a given characterexpression. The general syntax of Substring is as follows :

SUBSTRING(expression, start, length)
Here the function gets the string from start to length. Let us take an example below:

SELECT OUT = SUBSTRING('abcdefgh', 2, 3)

The output will be "bcd".
Note : substring also works on ntext, VARCHAR, CHAR etc.

LOWER / UPPER

Anoter simple but handy function is Lower / UPPER. The will just change case of a string expression. For Example,

SELECT UPPER('this is Lower TEXT') 

Output:
THIS IS LOWER TEXT