Sql Server\ MySql 日期

------------------MS Sql Server------------------

declare @ctrBeginTime =null;

if(@ctrBeginTime Is NUll)
begin
set @ctrBeginTime= GETDATE();
end

declare @statisticsDate as datetime = CONVERT(varchar(10),@ctrBeginTime,120); /*统计时间*/
declare @ThisYear1stDay as datetime = DATEADD(yy, DATEDIFF(yy,0,@statisticsDate),0); /*本年的第一天*/
declare @LastYearLastDay as datetime = DATEADD(dd,-1,@ThisYear1stDay); /*去年的最后一天*/
declare @LastYear1stDay as datetime = DATEADD(yy, DATEDIFF(yy,0,@LastYearLastDay),0); /*去年的第一天*/

set @beginTime = DATEADD(mm,DATEDIFF(mm,0,DATEADD(MONTH,-1,GETDATE())),0)--上月第一天
set @endTime = DATEADD(ms,-3,DATEADD(mm,DATEDIFF(mm,0,GETDATE()),0))--上月最后一天

CONVERT(char(6), GETDATA(),112)  as CourseDateYM

------------------MySQL------------------

DECLARE _DateTimeNow DATETIME DEFAULT NOW();
DECLARE _CurYear INT DEFAULT YEAR(CURRENT_DATE());
DECLARE _CurMonth INT DEFAULT MONTH(CURRENT_DATE());
DECLARE _Month_First_Day DATETIME default CAST(CONCAT(DATE_FORMAT(now(),"%Y.%m."),"01 00:00:00") AS datetime);
DECLARE _Month_Last_Day DATETIME default CAST(CONCAT(LAST_DAY(now())," 23:59:59") AS datetime);

SELECT str_to_date('2019-05-01','%Y-%m-%d')

SELECT CAST(CONCAT(DATE_FORMAT(str_to_date('2019-05-01','%Y-%m-%d'),"%Y.%m."),"01 00:00:00") AS datetime);

SELECT LAST_DAY(NOW()); #本月最后一天