双子座的鱼

1、DATEDIFF 计算日期差语法：DATEDIFF(datepart,startdate,enddate)查询当前时间：SELECT GETDATE()查询指定日期与当前日期的分钟差：SELECT DATEDIFF(MINUTE, '2019-10-08 16:10:00', GETDATE())秒差：SELECT DATEDIFF(ss, '2019-10-08 16:2...

1.UNION ALL列出所有的值，允许重复值方法一：select sum(a) from (select COUNT(*) a from IR union all select COUNT(*) a from HIST_IR) c方法二：select COUNT(*) from (select IR_ID from IR union all select IR_ID from HIST...