在 SQL Server 中默認情況下，每周的開始都是從周日開始算起的，如果默認星期一呢？

SET DATEFIRST 1   --定義日期周一開始 

三：直接寫一個函數，每次調用一下就可以了

SELECT @@DATEFIRST  --7
SELECT DATENAME(WEEK,‘2013-12-31‘) AS WeekName  -- 53
SELECT DATENAME(WEEK,‘2014-01-01‘) AS WeekName  -- 1
SELECT DATENAME(WEEK,‘2014-01-05‘) AS WeekName  -- 2

代碼：

1.創建表：

IF OBJECT_ID(‘DimDateStartWithMonday‘,‘U‘) IS NOT NULL
DROP TABLE DimDateStartWithMonday
GO

CREATE TABLE DimDateStartWithMonday
(
    DateKey INT PRIMARY KEY,
    FullDate DATE NOT NULL,
    [DateName] NVARCHAR(20),
    DayNumberOfWeek TINYINT NOT NULL,
    DayNameOfWeek NVARCHAR(10) NOT NULL,
    DayNumberOfMonth TINYINT NOT NULL,
    DayNumberOfYear SMALLINT NOT NULL, 
    WeekNumberOfYear TINYINT NOT NULL,
    EnglishMonthName NVARCHAR(10) NOT NULL,
    MonthNumberOfYear TINYINT NOT NULL,
    CalendarQuarter TINYINT NOT NULL,
    CalendarSemester TINYINT NOT NULL,
    CalendarYear SMALLINT NOT NULL 
)

2.插入值

DECLARE @StartDate DATETIME
DECLARE @EndDate DATETIME

SELECT @StartDate = ‘2001-01-01‘,
       @EndDate = ‘2035-12-31‘

	   WHILE(@StartDate<[email protected])
	   BEGIN
        INSERT INTO DimDateStartWithMonday 
    (
        DateKey,
        FullDate,
        [DateName],
        DayNumberOfWeek,
        DayNameOfWeek,
        DayNumberOfMonth,
        DayNumberOfYear, 
        WeekNumberOfYear,
        EnglishMonthName, 
        MonthNumberOfYear,
        CalendarQuarter,
        CalendarSemester,
        CalendarYear 
    )
    SELECT CAST(CONVERT(VARCHAR(8),@StartDate,112) AS INT) AS DateKey,
           CONVERT(VARCHAR(10), @StartDate,20) AS FullDate,
           CONVERT(VARCHAR(20), @StartDate,106) AS [DateName],
           DATEPART(DW,@StartDate) AS DayNumberOfWeek,
           DATENAME(DW,@StartDate) AS DayNameOfWeek,
           DATENAME(DD,@StartDate) AS [DayOfMonth],
           DATENAME(DY,@StartDate) AS [DayOfYear],  
           DATEPART(WW,@StartDate) AS WeekNumberOfYear,
           DATENAME(MM,@StartDate) AS EnglishMonthName,
           DATEPART(MM,@StartDate) AS MonthNumberOfYear,
           DATEPART(QQ,@StartDate) AS CalendarQuarter,
           CASE WHEN DATEPART(MM,@StartDate) BETWEEN 1 AND 6
                    THEN 1
                ELSE 2
           END AS CalendarSemester,
           DATEPART(YY,@StartDate) AS CalendarYear 
SET @StartDate = @StartDate + 1
	   END
       

3.自定義函數

	   IF OBJECT_ID(‘ETLWORK_GETWEEKNUMBER‘,‘FN‘) IS NOT NULL
DROP FUNCTION ETLWORK_GETWEEKNUMBER
GO
 
CREATE FUNCTION ETLWORK_GETWEEKNUMBER(@DATE DATETIME)  
RETURNS INTEGER
AS
BEGIN 
 DECLARE @FIRST_DATE_OF_YEAR DATETIME = DATEADD(YYYY,DATEDIFF(YYYY,0,@DATE),0) 

  DECLARE @WEEK_NUMBER INTEGER

    -- 如果當前時間是當前年的第一天
    IF @DATE = @FIRST_DATE_OF_YEAR
        SET @WEEK_NUMBER = 1 
    -- 星期天是年第一天的情況
    ELSE IF (DATEPART(WEEKDAY,@DATE) = 1 AND DATEDIFF(DAYOFYEAR,@FIRST_DATE_OF_YEAR,@DATE)/7 + 1 = DATEPART(WEEK,@DATE))  
        SET @WEEK_NUMBER = DATEPART(WEEK,@DATE)  
    -- 星期天不是年第一天的情況
    ELSE IF (DATEPART(WEEKDAY,@DATE) = 1 AND DATEDIFF(DAYOFYEAR,@FIRST_DATE_OF_YEAR,@DATE)/7 + 1 <> DATEPART(WEEK,@DATE)) 
        SET @WEEK_NUMBER = DATEPART(WEEK,@DATE) - 1 
    -- 如果當前天的上一個周日小於年第一天
    ELSE IF DATEADD(DAY,-1,DATEADD(WK,DATEDIFF(WK,0,@DATE),0)) < @FIRST_DATE_OF_YEAR 
        SET @WEEK_NUMBER = 1 
    -- 當前天前面的一個周日正好是以周日為開始年的 7 倍的天數
    ELSE IF DATEDIFF(DAYOFYEAR,@FIRST_DATE_OF_YEAR,DATEADD(DAY,-1,DATEADD(WK,DATEDIFF(WK,0,@DATE),0) ))/7 + 1 = DATEPART(WEEK,@DATE) 
        SET @WEEK_NUMBER = DATEPART(WEEK,@DATE) + 1  
    ELSE 
        SET @WEEK_NUMBER = DATEPART(WEEK,@DATE)   
           
    RETURN @WEEK_NUMBER
END

測試：

DECLARE @DATE DATETIME = ‘2017-01-02‘
DECLARE @FIRST_DATE_OF_YEAR DATETIME = DATEADD(YYYY,DATEDIFF(YYYY,0,@DATE),0) 

SELECT DATEPART(WEEK,@DATE), -- 一年中的周數，默認以周日開始 
       DATEADD(WK,DATEDIFF(WK,0,@DATE),0), -- 當前周的周一，默認從周日開始，但是仍然找周一
       DATEADD(DAY,-1,DATEADD(WK,DATEDIFF(WK,0,@DATE),0)), -- 當前周先找周一，然後往前一天找到周日
       DATEDIFF(DAYOFYEAR,@FIRST_DATE_OF_YEAR,DATEADD(DAY,-1,DATEADD(WK,DATEDIFF(WK,0,@DATE),0))), -- 當前天離年第一天的間隔
       DATEDIFF(DAYOFYEAR,@FIRST_DATE_OF_YEAR,DATEADD(DAY,-1,DATEADD(WK,DATEDIFF(WK,0,@DATE),0) ))/7 + 1  -- 按天計算的周數

SqlServer中 SET DATEFIRST更改