Wednesday, 31 October 2007

Parse delimited string in a Stored procedure

Sometimes we need to pass an array to the Stored Procrdure and split the array inside the stored proc. For example, lets say there is a datagrid displaying sales orders, each sales order associated with an orderid (PK in the Sales table). If the user needs to delete a bunch of sales orders ( say 10-15 etc) would be easier to concatenate all the orderid's into one string like 10-24-23-34-56-57-....etc and pass it to the sql server stored proc and inside the stored proc, split the string into individual ids and delete each sales order.
There can be plenty of other situations where passing a delimited string to the stored proc is faster than making n number of trips to the server.

CREATE PROCEDURE ParseArray (@Array VARCHAR(1000),@separator CHAR(1))
-- @Array is the array we wish to parse
-- @Separator is the separator charactor such as a comma
DECLARE @separator_position INT -- This is used to locate each separator character
DECLARE @array_value VARCHAR(1000) -- this holds each array value as it is returned
-- For my loop to work I need an extra separator at the end. I always look to the
-- left of the separator character for each array value
SET @array = @array + @separator
-- Loop through the string searching for separtor characters
WHILE PATINDEX('%' + @separator + '%', @array) <> 0
-- patindex matches the a pattern against a string
SELECT @separator_position = PATINDEX('%' + @separator + '%',@array)
SELECT @array_value = LEFT(@array, @separator_position - 1)
-- This is where you process the values passed.
-- Replace this select statement with your processing
-- @array_value holds the value of this element of the array
SELECT Array_Value = @array_value
-- This replaces what we just processed with and empty string
SELECT @array = STUFF(@array, 1, @separator_position, '')

The credit for the above code : Mr Dinakar Nethi on his blog

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