CREATE FUNCTION

Syntax#

CREATE FUNCTION function_name ( [list_of_paramenters] ) RETURNS return_data_type

AS BEGIN function_body RETURN scalar_expression END

Parameters#

Argument	Description
function_name	the name of function
list_of_paramenters	parameters that function accepts
return_data_type	type that function returs. Some SQL data type
function_body	the code of function
scalar_expression	scalar value returned by function

Remarks#

CREATE FUNCTION creates a user-defined function that can be used when doing a SELECT, INSERT, UPDATE, or DELETE query. The functions can be created to return a single variable or a single table.

Create a new Function

CREATE FUNCTION FirstWord (@input varchar(1000))
RETURNS varchar(1000)
AS
BEGIN
    DECLARE @output varchar(1000)
    SET @output = SUBSTRING(@input, 0, CASE CHARINDEX(' ', @input)
        WHEN 0 THEN LEN(@input) + 1
        ELSE CHARINDEX(' ', @input)
    END)

    RETURN @output
END

This example creates a function named FirstWord, that accepts a varchar parameter and returns another varchar value.