sql - 如何使此语句更快 : "paramDate Between startDate and NULL"?

Question

当 endDate 为 null 时，此查询需要很长时间(我认为它是关于 case 语句，在 case 语句之前它很快)

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

当 endDate 为空时，我应该使用什么来加快速度？

Answer 1

这是没有 CONVERT 或 CASE 的查询:

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

为了确保 Sql Server 不会对每一行计算 getdate()，您可以缓存它，尽管我很确定 Sql Server 默认情况下足够智能:

declare @now datetime
set @now = getdate()

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

发布查询计划可以帮助解释查询速度慢的原因:

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)