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Posted by Plamen Ratchev on 01/29/08 14:48
You cannot directly reference an aliased column in the same SELECT
statement, you would have to repeat the expression. However, you can use a
derived table (or a Common Table Expression if on SQL Server 2005 -
http://msdn2.microsoft.com/en-us/library/ms190766.aspx). Here is an example
using derived table:
SELECT elapsed_days,
CASE WHEN elapsed_days > 60
THEN 'Over 60 days'
ELSE 'Less than 60 days'
END AS msg
FROM (SELECT CASE
WHEN 1 = 1
THEN DATEDIFF(dd, '20080118', '20080120')
END
) AS T (elapsed_days)
HTH,
Plamen Ratchev
http://www.SQLStudio.com
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