The MSDN is a good reference for these type of questions regarding syntax and usage. This is from the Transact SQL Reference - CASE page. ... <看更多>

SELECT dbo.tPerson.pNameLast, CASE WHEN tApplication.aDeptChair IS NOT NULL THEN CASE WHEN tApplication.aDeptChair <> 0 THEN. ''subquery 1. ... <看更多>

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The key is that the CASE expression is only ever going to return 3 (or ... The original query in the question has an issue: SQL Server is ... ... <看更多>