Using a CTE in a Function to Split Up a Query String

The question came up as to how do I parse a query string using TSQL.  So here you go, using a common table expression, and basing this on a similar function to what I put together yesterday for split.

CREATE FUNCTION dbo.SplitQueryString (@s varchar(8000))
RETURNS table
AS
RETURN (
 WITH splitter_cte AS (
 SELECT CHARINDEX('&', @s) as pos, 0 as lastPos
 UNION ALL
 SELECT CHARINDEX('&', @s, pos + 1), pos
 FROM splitter_cte
 WHERE pos > 0
 ),
 pair_cte AS (
 SELECT chunk,
 CHARINDEX('=', chunk) as pos
 FROM (
 SELECT SUBSTRING(@s, lastPos + 1,
 case when pos = 0 then 80000
 else pos - lastPos -1 end) as chunk
 FROM splitter_cte) as t1
 )
 SELECT substring(chunk, 0, pos) as keyName,
 substring(chunk, pos+1, 8000) as keyValue
 FROM pair_cte
)
GO

declare @queryString varchar(2048)
set @queryString = 'foo=bar&temp=baz&key=value';
SELECT *
 FROM dbo.SplitQueryString(@queryString)
OPTION(MAXRECURSION 0);

which produces this output.

A quick and easy way to parse a query string  in TSQL using a CTE.

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