数据库之SQL技巧整理案例

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

DECLARE @RQ SMALLDATETIME
SET @RQ = '2019-09-01';

;WITH
  tAppDays (fDay) AS
  (
    SELECT @RQ AS fDay
    UNioN ALL
    SELECT fDay + 1 FROM tAppDays WHERE DateDiff(Month,fDay+1,@RQ) = 0
  )
SELECT * FROM tAppDays ORDER BY fDAY

-- 利用递归来获得给定字符串的SPLIT方法

DECLARE @CommentStr NVARCHAR(4000)='总经理室|销售部|会计部|人事部|工会|后勤部|生产计划部|动力分厂|质量检验部|运输部'
DECLARE @Split     NVARCHAR(1)='|';

WITH Temp AS
(  SELECT 1 AS Num UNION ALL
   SELECT Num + 1
   FROM TEMP WHERE Num<Len(@CommentStr)   )
SELECT
  RN = Row_Number() Over(ORDER BY Num),
  SplitStr = SUBSTRING(@CommentStr,Num,CHARINDEX(@Split,@CommentStr+@Split,Num)-Num)
FROM Temp WHERE SUBSTRING(@Split+@CommentStr,Num,1) = @Split OPTION(MAXRECURSION 0);

--================================================================================================
--   pAppGetSplit '|','科目名称|身份证号|学员姓名|教练编号|教练姓名|培训次数|合计次数|负责比例'
================================================================================================
IF EXISTS (SELECT name FROM sysobjects WHERE name = 'pAppGetSplit' AND type = 'P')
   DROP PROCEDURE pAppGetSplit
Go
CREATE PROCEDURE pAppGetSplit
  @Split             VARCHAR(1),
  @STR               NVARCHAR(4000)
AS
  ;WITH Temp AS     -- 根据分隔符|获得字段列表
  (  SELECT 1 AS Num UNION ALL
     SELECT Num + 1
     FROM TEMP WHERE Num<Len(@STR)   )
  SELECT
    RN = Row_Number() Over(ORDER BY Num),
    SplitStr = SUBSTRING(@STR,Num,CHARINDEX(@Split,@STR+@Split,Num)-Num)
  FROM Temp WHERE SUBSTRING(@Split+@STR,Num,1) = @Split OPTION(MAXRECURSION 0);
GO

--获得本周周一的日期
DECLARE @Z SMALLINT
-- [1,2,3,4,5,6,7]分别代表[周一,周二,周三,周四,周五,周六,周日]
SET @Z=1
SELECT
  GetDate() 今天,
  DATEPART(Weekday,GetDate()) 今天序号,
  (DATEPART(Weekday,GetDate()) + @@DATEFIRST-1)%7 今天是周几,
  DATEADD(Day,@Z-(DATEPART(Weekday,GetDate()) + @@DATEFIRST-1)%7,GetDate()) 本周周一