一、獲得給定月份的周日數(shù)

根據(jù)給定的某個(gè)日期，計(jì)算這個(gè)月份的周日的天數(shù)。
根據(jù)系統(tǒng)變量@@DATEFIRST的值，判斷周日的序號(hào)為【DatePart(WEEKDAY,RQ)= (07-@@DateFirst) % 7 + 1】。下面列出了周日、周一…周六的公式

下面是獲得周日的SQL語(yǔ)句，SQL語(yǔ)句采用了嵌套循環(huán)的方式來(lái)獲取數(shù)據(jù)

DECLARE @Day SmallDateTime
SET @Day = DateAdd(MM, DateDiff(MM,0,’2019-11-21′), 0)

;WITH Temp AS
( SELECT @Day AS RQ UNION ALL
SELECT RQ+1
FROM TEMP WHERE DateDiff(Month,RQ+1,@Day) = 0
)
SELECT
RN = Row_Number() Over(ORDER BY RQ),
RQ
FROM Temp WHERE DatePart(WEEKDAY,RQ)= (07-@@DateFirst) % 7 + 1