Query to compare cast in select statement - sql

Question

I have a query where I am pulling in three fields, and converting them to a date. I'm hoping to then run a comparison within the same select statement, but I get an invalid column name on the field I'm attempting to compare. The order by is working correctly though. /scratching_head
SQL Server 2012
SELECT
UTCSID,
UTLCID,
/* put utonmm, utondd, utonyy together as a date called uton */
CAST(
CAST(UTONMM as varchar) + '/' +
CAST(UTONDD as varchar) + '/' +
CASE WHEN UTONCV = '1'
THEN RIGHT('20' + CONVERT(varchar(4), RIGHT('00' + CONVERT(varchar(4), UTONYY),2)),4)
ELSE RIGHT('19' + CONVERT(varchar(4), UTONYY),4)
END
AS DATETIME) AS UTON,
/* put utofmm, utofdd, utofyy together as a date called utoff */
CAST(
CASE WHEN UTOFMM > '0'
THEN
CAST(UTOFMM as varchar) + '/' +
CAST(UTOFDD as varchar) + '/' +
CASE WHEN UTOFCV = '1'
THEN RIGHT('20' + CONVERT(varchar(4), RIGHT('00' + CONVERT(varchar(4), UTOFYY),2)),4)
ELSE RIGHT('19' + CONVERT(varchar(4), UTOFYY),4)
END
END
AS DATETIME) AS UTOFF,
UTCBAL,
UTDBAL,
UTUNPS
FROM [HTEDTA].[THOR].[HTEDTA].UT210AP
WHERE UTLCID = '885570' AND UTOFF > GETDATE() ORDER BY UTON DESC
This statement returns:
Invalid column name: 'UTOFF'

Answer 1

The problem is that the alias utoff isn't known at the time when the where clause is parsed.
One way to get around it is to wrap the query in a common table expression and apply the where clause to that:
WITH CTE AS (
SELECT UTCSID, UTLCID,
/* put utonmm, utondd, utonyy together as a date called uton */
CAST(
CAST(UTONMM as varchar) + '/' +
CAST(UTONDD as varchar) + '/' +
CASE WHEN UTONCV = '1'
THEN RIGHT('20' + CONVERT(varchar(4), RIGHT('00' + CONVERT(varchar(4), UTONYY),2)),4)
ELSE RIGHT('19' + CONVERT(varchar(4), UTONYY),4)
END
AS DATETIME) AS UTON,
/* put utofmm, utofdd, utofyy together as a date called utoff */
CAST(
CASE WHEN UTOFMM > '0'
THEN
CAST(UTOFMM as varchar) + '/' +
CAST(UTOFDD as varchar) + '/' +
CASE WHEN UTOFCV = '1'
THEN RIGHT('20' + CONVERT(varchar(4), RIGHT('00' + CONVERT(varchar(4), UTOFYY),2)),4)
ELSE RIGHT('19' + CONVERT(varchar(4), UTOFYY),4)
END
END
AS DATETIME) AS UTOFF,
UTCBAL, UTDBAL, UTUNPS
FROM [HTEDTA].[THOR].[HTEDTA].UT210AP
)
SELECT *
FROM CTE
WHERE UTLCID = '885570' AND UTOFF > GETDATE()