MYSQL 自定义函数（if else）
IF OBJECT_ID('dbo.GetDateDiff', 'FN') IS NOT NULL OR OBJECT_ID('dbo.GetDateDiff', 'TF') IS NOT NULL OR OBJECT_ID('dbo.GetDateDiff', 'IF') IS NOT NULL DROP FUNCTION dbo.GetDateDiff //判断此函数是否存在，若存在，删除，不存在，重建 GO create function GetDateDiff(@start varchar(200),@end varchar(200),@t_start varchar(200),@t_end varchar(200)) returns @d table(time varchar(20)) //建立临时表，returns确定返回值类型 as //函数写在begin,end 中 begin declare @result int,@Max varchar(200),@Min varchar(200) //定义变量 if(DATEDIFF(day,@start,@t_start)>0) //判断两个时间的大小 set @Max=@t_start else set @Max=@start if(DATEDIFF(day,@end,@t_end)>0) set @Min=@end else set @Min=@t_end if(DATEDIFF(day,@t_start,@end) <0) set @result=0 else if(@end is not null) set @result=DATEDIFF(day,@Max,@Min) //返回两个时间的差值 else set @result=DATEDIFF(day,@Max,@t_end) insert into @d(time) values (@result) //结果插入表中 return end GO COMMIT
GO
select * from gEtdatediff('2015-02-12',null,'2013-03-24','2015-05-24') //调用此函数