When SQL functions were first introduced I stumbled across one function in particular that I’ve probably used more than any other. In fact, I doubt I’ve developed too many databases that didn’t use this great little function. It’s really quite simple… but very, very powerful. It’s called… fn_ParseCommaDelimitedList. This simple yet powerful little function allows you to pass in a comma delimited list of integers for use when querying a subset of rows from a table.
You’ve got a table of employees and a simple list of ids of a subset of those employees. You need to return just the employee information of the subset of employees.
DECLARE @IDList varchar(2000)
SET @IDList = ‘1,2,3,4,5,6,7,8,9,10’
FROM Employee e
JOIN dbo.fn_ParseCommaDelimitedList(@IDList) ids ON (e.EmployeeID = ids.ItemID)
So simple. So easy. So darn convenient.
ALTER FUNCTION dbo.fn_ParseCommaDelimitedList
RETURNS @TableVar TABLE (ItemID int NOT NULL )
DECLARE @IDListPosition int
DECLARE @IDList varchar(4000)
DECLARE @ArrValue varchar(4000)
SET @IDList = COALESCE(@CommaDelimitedList, '')
IF @IDList <> ''
-- Add comma to end of list so user doesn't have to
SET @IDList = @IDList + ','
-- Loop through the comma demlimted string list
WHILE PATINDEX('%,%' , @IDList ) <> 0
SELECT @IDListPosition = PATINDEX('%,%' , @IDList)
SELECT @ArrValue = LEFT(@IDList, @IDListPosition - 1)
-- Insert parsed ID into TableVar for "where in select"
INSERT INTO @TableVar (ItemID) VALUES (CONVERT(int, @ArrValue))
-- Remove processed string
SELECT @IDList = STUFF(@IDList, 1, @IDListPosition, '')
Put it to use. Anyone else have a function they just can't live without?