Convert和Datediff日期转换函数效率对比(第一次发帖)

select a.staffId,B.Name,

sum(case day(a.ProduceDate) when '1'  then a.complement+a.ProduceTime else 0 end)'1',

sum(case day(a.ProduceDate) when '2'  then a.complement+a.ProduceTime else 0 end)'2',

............

sum(case day(a.ProduceDate) when '31' then a.complement+a.ProduceTime else 0 end)'31'

from dbo.ProduceTimeBomForMaster a left join [MRP.NET.DB].dbo.Staff B

on a.staffId collate Chinese_PRC_CI_AS =  B.StaffID collate Chinese_PRC_CI_AS

where datediff(month,ProduceDate,'2010-06-01') = 0--耗时2秒

--where convert(varchar(7),ProduceDate,120) ='2010-06' --耗时7秒

group by a.staffId,B.Name

在行转列中,查询条件用Convert(varchar(7),ProduceDate,120)来查询，查询结果集耗时7秒，

用Datediff（ProduceDate，'2010-06'）来查询结果集耗时2秒，

在相同的条件下datediff的效率高很多。