sql_笔记

Declare @DayOne DateTime--按天,今天SET @DayOne = DATEADD (dd, DATEDIFF (dd, 0, getdate ()), 0)--按周,周的第一天SET @DayOne = DATEADD (wk, DATEDIFF (wk, 0, getdate ()), 0)--按月,月的第一天SET @DayOne = DATEADD (mm, DATEDIFF (mm, 0, getdate ()), 0)--连接删除例子:Delete aFrom tableA aLeft Join TableB bOn a.XXX = b.XXXWhere a.YYY='yyy'