Question

This query is taking long time when endDate is null (i think that its about case statement, before case statement it was fast)

SELECT * 
FROM HastaKurumlari
WHERE CONVERT(SMALLDATETIME,'21-05-2009',103) 
BETWEEN startDate 
    AND (CASE WHEN endDate IS NULL THEN GETDATE() ELSE endDate END) 

What should i use, when endDate is null to make it faster ?

Answer 1

Here’s the query without CONVERT or CASE:

SELECT * 
FROM HastaKurumlari
WHERE '21-05-2009' between startDate and IsNull(endDate,getdate())

To make sure Sql Server doens’t evaluate getdate() for every row, you could cache it, although I’m pretty sure Sql Server is smart enough by default:

declare @now datetime
set @now = getdate()

SELECT * 
FROM HastaKurumlari
WHERE '21-05-2009' between startDate and IsNull(endDate,@now)

Posting the query plan could help explain why the query is slow:

SET SHOWPLAN_TEXT ON
go
SELECT * 
FROM HastaKurumlari
WHERE CONVERT(SMALLDATETIME,'21-05-2009',103) 
BETWEEN startDate 
    AND (CASE WHEN endDate IS NULL THEN GETDATE() ELSE endDate END)