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最快方法：SELECT top 1 @count=1,同时item_urlkey字段做了聚集索引或非聚集索引
如果语句执行时，不走索引的话，也可以用with(index=IX_t2_col1)指定索引，例如：select * from t2 with(index=IX_t2_col1) where col1=201
GOdeclare @num int declare @beforDateTime datetime declare @count int set @num=0;set @beforDateTime=GETDATE()while (@num<100000)begin set @count=0 SELECT top 1 @count=1 FROM [iWOMTrackData].[dbo].[SEC_Item] WHERE [Item_URLKey]='e6d71e8d1c410cd84317897be0d0b5b6' set @num=@num+1endprint datediff(MILLISECOND,@beforDateTime,GETDATE())
其他方法1：SELECT top 1 @count=COUNT(主键)
/****** Script for SelectTopNRows command from SSMS ******/GOdeclare @num int declare @beforDateTime datetime declare @count int set @num=0;set @beforDateTime=GETDATE()while (@num<100000)begin set @count=0 SELECT top 1 @count=COUNT(item_id) FROM [iWOMTrackData].[dbo].[SEC_Item] WHERE [Item_URLKey]='e6d71e8d1c410cd84317897be0d0b5b6' set @num=@num+1endprint datediff(MILLISECOND,@beforDateTime,GETDATE())
其他方法2：SELECT top 1 @count=COUNT(*)
/****** Script for SelectTopNRows command from SSMS ******/GOdeclare @num int declare @beforDateTime datetime declare @count int set @num=0;set @beforDateTime=GETDATE()while (@num<100000)begin set @count=0 SELECT top 1 @count=COUNT(*) FROM [iWOMTrackData].[dbo].[SEC_Item] WHERE [Item_URLKey]='e6d71e8d1c410cd84317897be0d0b5b6' set @num=@num+1endprint datediff(MILLISECOND,@beforDateTime,GETDATE())其他方法3：SELECT top 1 @count=COUNT(1)
/****** Script for SelectTopNRows command from SSMS ******/GOdeclare @num int declare @beforDateTime datetime declare @count int set @num=0;set @beforDateTime=GETDATE()while (@num<100000)begin set @count=0 SELECT top 1 @count=COUNT(1) FROM [iWOMTrackData].[dbo].[SEC_Item] WHERE [Item_URLKey]='e6d71e8d1c410cd84317897be0d0b5b6' set @num=@num+1endprint datediff(MILLISECOND,@beforDateTime,GETDATE())其中select top 1 1 形式是最快的，其他三种方法的速度都差不多。
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