SQL Server ÈÕÆÚ²Ù×÷È«½Ó´¥

DECLARE @dt datetime
SET @dt=GETDATE()
DECLARE @number int
SET @number=3
--1£®Ö¸¶¨ÈÕÆÚ¸ÃÄêµÄµÚÒ»Ìì»ò×îºóÒ»Ìì
--A. ÄêµÄµÚÒ»Ìì
SELECT CONVERT(char(5),@dt,120)+'1-1'
--B. ÄêµÄ×îºóÒ»Ìì
SELECT CONVERT(char(5),@dt,120)+'12-31'
--2£®Ö¸¶¨ÈÕÆÚËùÔÚ¼¾¶ÈµÄµÚÒ»Ìì»ò×îºóÒ»Ìì
--A. ¼¾¶ÈµÄµÚÒ»Ìì
SELECT CONVERT(datetime,
    CONVERT(char(8),
        DATEADD(Month,
            DATEPART(Quarter,@dt)*3-Month(@dt)-2,
            @dt),
        120)+'1')
--B. ¼¾¶ÈµÄ×îºóÒ»Ì죨CASEÅжϷ¨£©
SELECT CONVERT(datetime,
    CONVERT(char(8),
        DATEADD(Month,
            DATEPART(Quarter,@dt)*3-Month(@dt),
            @dt),
        120)
    +CASE WHEN DATEPART(Quarter,@dt) in(1,4)
        THEN '31'ELSE '30' END)
--C. ¼¾¶ÈµÄ×îºóÒ»Ì죨ֱ½ÓÍÆËã·¨£©
SELECT DATEADD(Day,-1,
    CONVERT(char(8),
        DATEADD(Month,
            1+DATEPART(Quarter,@dt)*3-Month(@dt),
            @dt),
        120)+'1')
--3£®Ö¸¶¨ÈÕÆÚËùÔÚÔ·ݵĵÚÒ»Ìì»ò×îºóÒ»Ìì
--A. ÔµĵÚÒ»Ìì
SELECT CONVERT(datetime,CONVERT(char(8),@dt,120)+'1')
--B. ÔµÄ×îºóÒ»Ìì
SELECT DATEADD(Day,-1,CONVERT(char(8),DATEADD(Month,1,@dt),120)+'1')
--C. ÔµÄ×îºóÒ»Ì죨ÈÝÒ×ʹÓõĴíÎó·½·¨£©
SELECT DATEADD(Month,1,DATEADD(Day,-DAY(@dt),@dt))
--4£®Ö¸¶¨ÈÕÆÚËùÔÚÖܵÄÈÎÒâÒ»Ìì
SELECT DATEADD(Day,@number-DATEPART(Weekday,@dt),@dt)
--5£®Ö¸¶¨ÈÕÆÚËùÔÚÖܵÄÈÎÒâÐÇÆÚ¼¸
--A.  ÐÇÆÚÌì×öΪһÖܵĵÚ1Ìì
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