Join using dynamic column names SQL Server - sql

Question

I have a table which can output any number of different columns (from 'Level1' to 'Level'N).
I need to perform a left join on each of these dynamic columns against a CTE
I have written the following script but keep getting this error:
Msg 102, Level 15, State 1, Line 15 Incorrect syntax near '10'.
To troubleshoot, I have tried removing the each of the variables in the CTE with no luck.
Any help would be much appreciated!
DECLARE #rel varchar(4) = CAST('X112' AS varchar(4))
DECLARE #todaysdate date = CONVERT(date,GETDATE())
--create cte
DECLARE #sqltext varchar(MAX) =
' WITH CTE AS
(
SELECT
ID
,STARTDATE
,ENDDATE
,NEWID
FROM Tbl
WHERE TYPE = ''' + #rel + '''
AND ENDDATE >= ' + CAST(#todaysdate AS varchar(30)) +' AND STARTDATE <= ' + CAST(#todaysdate AS varchar(30)) +'
)
SELECT ID, NEWID, Level';
--find max lvl, convert to str
DECLARE #counter int = (SELECT MAX(lvl) FROM tbl2)
DECLARE #counterstring varchar(3)
SET #counterstring = CAST(#counter AS varchar(3))
WHILE #counter != 0
BEGIN
SET #sqltext = #sqltext + #counterstring + ' INTO tbl3 '
+ ' FROM tbl2 a '
+ ' LEFT JOIN CTE c ON a.Level' + #counterstring + ' = c.NEWID'
SET #counter = #counter - 1
END
EXEC(#sqltext)
--edited version
DECLARE #rel varchar(4) = CAST('X112' AS varchar(4))
DECLARE #todaysdate date = CONVERT(date,GETDATE())
DECLARE #sqltext varchar(MAX) =
' WITH CTE AS
(
SELECT
ID
,STARTDATE
,ENDDATE AS mgmt_ENDDA
,NEWID
FROM tbl
WHERE SUBTY = ''' + #rel + '''
AND ENDDATE >= ' + CAST(#todaysdate AS varchar(30)) +' AND STARTDATE <= ' + CAST(#todaysdate AS varchar(30)) +'
)
INSERT INTO tbl3
SELECT ID, NEWID, Level';
DECLARE #counter int = (SELECT MAX(lvl) FROM tbl2)
DECLARE #counterstring varchar(3)
WHILE #counter != 0
BEGIN
SET #counterstring = CAST(#counter AS varchar(3))
SET #sqltext = #sqltext + #counterstring
+ ' FROM tbl2 a '
+ ' LEFT JOIN CTE c ON a.Level' + #counterstring + ' = c.NEWID'
SET #counter = #counter - 1
END
EXEC(#sqltext)

Answer 1

Since select * into query creates a new table each time, I am assuming that you are trying to create 'n' number of tables for 'n' number of levels, with the result obtained by joining with nth column. I have 2 suggestions for you
Bring the select query within the while loop and append ';' at the end of the loop to split select queries.
instead of INTO tbl3 use INTO tbl + #counterstring as select * into will create new table
Hope this helps you

Answer 2

Can you change it like this and try again?
--edited version
DECLARE #rel varchar(4) = CAST('A012' AS varchar(4))
DECLARE #todaysdate date = CONVERT(date,GETDATE())
DECLARE #sqltext varchar(MAX) =
' WITH CTE AS
(
SELECT
ID
,STARTDATE
,ENDDATE AS mgmt_ENDDA
,NEWID
FROM tbl
WHERE SUBTY = ''' + #rel + '''
AND ENDDATE >= ' + CAST(#todaysdate AS varchar(30)) +' AND STARTDATE <= ' + CAST(#todaysdate AS varchar(30)) +'
)
INSERT INTO tbl3';
DECLARE #counter int = (SELECT MAX(lvl) FROM tbl2)
DECLARE #counterstring varchar(3)
WHILE #counter != 0
BEGIN
SET #counterstring = CAST(#counter AS varchar(3))
SET #sqltext = #sqltext + CHAR(10) +'SELECT ID, NEWID, Level'+#counterstring
SET #sqltext = #sqltext + ' FROM tbl2 a '
+ ' LEFT JOIN CTE c ON a.Level' + #counterstring + ' = c.NEWID'
SET #counter = #counter - 1
IF #counter <> 0
SET #sqltext = #sqltext + CHAR(10) + ' UNION '
END
EXEC(#sqltext)
You can try 'UNION ALL' instead of 'UNION' if you dont want to get rid of duplicate data. Hope this helps