subquery with table value function not working - sql-server

Question

DECLARE #temp AS TABLE (id INT, NAME VARCHAR(20) )
DECLARE #str VARCHAR(20) = '1,2'
INSERT INTO #temp (id, NAME)
VALUES (1, ''), (2, ''), (2, '')
SELECT *
FROM #temp a
WHERE id IN ((SELECT String FROM dbo.FN_SplitStrings(#str,',')))
I'm getting the following error while running this
Conversion failed when converting the varchar value '1,2' to data type
int.
Code:
CREATE function [dbo].[FN_SplitStrings]
(
#StringToSplit varchar(8000),
#Separator varchar(128)
)
RETURN TABLE
AS
RETURN
with indices as
(
select
0 S, 1 E
union all
select
E, charindex(#Separator, #StringToSplit, E) + len(#Separator)
from
indices
where E > S
)
select
substring(#StringToSplit,S, case when E > len(#Separator)
then e-s-len(#Separator) else len(#StringToSplit) - s + 1 end) String ,
S StartIndex
from
indices
where
S > 0

Answer 1

Try this. This splitting can be used without a function
DECLARE #temp AS TABLE
(
id INT,
NAME VARCHAR(20)
)
DECLARE #str VARCHAR(20)='1,2'
INSERT INTO #temp
( id, NAME )
VALUES ( 1, '' ),
( 2, ''),
( 2, '')
SELECT * FROM #temp a
WHERE id IN
(
SELECT LTRIM(RTRIM(Split.a.value('.', 'VARCHAR(100)'))) 'KeyWords'
FROM
(
-- To change ',' to any other delimeter, just change ',' before '</M><M>' to your desired one
SELECT CAST ('<M>' + REPLACE(#str, ',', '</M><M>') + '</M>' AS XML) AS Data
) AS A
CROSS APPLY Data.nodes ('/M') AS Split(a)
)
Click here to view the result
EDIT:
You had some problems in function for splitting.
Function
ALTER FUNCTION dbo.FN_SplitStrings(#StringToSplit varchar(8000),#Separator char(1))
RETURNS table
AS
RETURN (
WITH splitter_cte AS (
SELECT CHARINDEX(#Separator, #StringToSplit) as pos, 0 as lastPos
UNION ALL
SELECT CHARINDEX(#Separator, #StringToSplit, pos + 1), pos
FROM splitter_cte
WHERE pos > 0
)
SELECT SUBSTRING(#StringToSplit, lastPos + 1,
case when pos = 0 then 80000
else pos - lastPos -1 end) as String
FROM splitter_cte
)
Query
DECLARE #temp AS TABLE (id INT, NAME VARCHAR(20) )
DECLARE #str VARCHAR(20) = '1,2'
INSERT INTO #temp (id, NAME)
VALUES (1, ''), (2, ''), (2, '')
SELECT *
FROM #temp a
WHERE id IN ((SELECT String FROM dbo.FN_SplitStrings(#str,',')))
Click here to view result

Answer 2

The reason is a mix in data types and the fact that your function is an inline table valued functions which means that it is embedded into the query before query optimization takes place.
If you remove where S > 0 from your function and execute it with 1,2, the result of the function is:
String
------
1,2
1
2
Notice the first row where the value is 1,2.
When the optimizer does its job with your query the comparison against the column id is done before the where clause of the function is evaluated. In that comparison you have an implicit cast to int and 1,2 can not be casted to an int.
To fix this you can make sure that the String column of your split function is always an int (and perhaps changing the name of the column in the process).
select
cast(substring(#StringToSplit,S, case when E > len(#Separator)
then e-s-len(#Separator)
else len(#StringToSplit) - s + 1
end) as int) String ,