Split Comma seperated value other than split function - sql

Question

FOR EACH LINE THERE IS AN VALID Patient_id ASSOCIATED WITH IT in Parent table
i try to validate whether correct Patient_id linked with line.
problem:
In child table Patient_id is comma seperated.
if i am using function to split value, the query is not completing even after
15 hours.
can anyone suggest some other alternate, without using finction Please if possible
DECLARE #PARENT_TABLE TABLE
(
Line VARCHAR (50),
Patient_id VARCHAR (50)
)
INSERT #PARENT_TABLE
SELECT 'ABSRB', 'E001' UNION ALL
SELECT 'ABSRB', 'E067' UNION ALL
SELECT 'ABSRB', 'E068'
DECLARE #CHILD_TABLE TABLE
(
LINE VARCHAR (50),
SKU VARCHAR (50),
Patient_id VARCHAR (50)
)
INSERT #CHILD_TABLE
SELECT 'ABSRB', 'PRS317580', NULL UNION ALL
SELECT 'ABSRB', 'RANRS7371', 'E001' UNION ALL
SELECT 'ABSRB', 'KYBKG54327', 'E067' UNION ALL
SELECT 'ABSRB', 'KYB344615', 'V048, V055, E068' UNION ALL
SELECT 'ABSRB', 'ZZZZ15245', 'S128, V048, V055'
SELECT * FROM #CHILD_TABLE
can anyone suggest some other alternate, without using finction Please if possible
i have not included split function code here.
Code:
CREATE FUNCTION [dbo].[fnSplitString](
#string NVARCHAR(MAX),
#delimiter CHAR(1),
#keylist nvarchar(50))
RETURNS TABLE
AS
RETURN(
WITH CTE AS(
SELECT 1 as n
UNION ALL
SELECT 1
UNION ALL
SELECT 1
UNION ALL
SELECT 1
UNION ALL
SELECT 1
UNION ALL
SELECT 1
UNION ALL
SELECT 1
UNION ALL
SELECT 1
UNION ALL
SELECT 1
UNION ALL
SELECT 1
),CTE2 AS(
SELECT ROW_NUMBER() OVER(ORDER BY c.n) as n
FROM CTE c
CROSS JOIN CTE c2
CROSS JOIN CTE c3
CROSS JOIN CTE c4
CROSS JOIN CTE c5
CROSS JOIN CTE c6
)
SELECT TOP(LEN(COALESCE(#string,'')))
splitdata = ltrim(rtrim(
SUBSTRING(#string, n, CHARINDEX(#delimiter, #string + #delimiter, n)-n)
)),
keyname= #keylist
FROM CTE2
WHERE n<= LEN(#string)
AND SUBSTRING(#Delimiter + #string , n, LEN(#Delimiter)) = #Delimiter
)
DECLARE #SplittedTable TABLE
(
splitted VARCHAR (50),
keys VARCHAR (50)
)
INSERT INTO #SplittedTable(splitted,keys)
SELECT ss.splitdata, ss.keyname
FROM #CHILD_TABLE ct
CROSS APPLY dbo.fnSplitString(ct.Patient_id,',',ct.Patient_id) ss
SELECT * FROM #CHILD_TABLE ct WHERE ct.Patient_id IN (
SELECT DISTINCT st.keys
FROM #SplittedTable AS st
WHERE st.splitted NOT IN (SELECT Patient_id FROM #Parent_table m ));
SELECT DISTINCT ct.*
FROM #CHILD_TABLE ct
CROSS APPLY dbo.fnSplitString(ct.Patient_id,',',ct.Patient_id) ss
WHERE ss.splitdata NOT IN (SELECT Patient_id FROM #Parent_table)
The below code took more than 15 hours to execute. table size: 20GB
CODE:
--selecting by keys and finding them into master
SELECT * FROM #child ct WHERE ct.patientid IN (
SELECT DISTINCT st.keys
FROM #SplittedTable AS st
WHERE st.splitted NOT IN (SELECT patientid FROM #parent m ));
--Use CROSS APPLY to get this done for all rows.
SELECT DISTINCT ct.*
FROM #child ct
CROSS APPLY dbo.fnSplitString(ct.patientid,',',ct.patientid) ss
WHERE ss.splitdata NOT IN (SELECT patientid FROM #parent)