Question

我有一个包含CRON表达式的列，该表达式表示用户执行任务的频率。我想构建一个视图，列出给定用户的日期和事情。但我需要在T-SQL中的日期时间计算我的下一个CRON事件。如何在SQL中解释我的CRON表达式？

例如：列值= [0 30 8 1 *？]

我会写： SELECT CrontabSchedule（'0 30 8 1 *？'，GETDATE（））FROM dbo.UserTasks

有人有解决方案吗？

Answer 1

也许这个链接可以给你一个提示：https://ask.sqlservercentral.com/questions/117285/tsql-sql-function-for-a-cron-expression.html

链接中显示的UDF如下：

CREATE PROCEDURE Q117285.CreateJobScheduleFromCronExpression
     @CronExpression varchar(200)
     , @FieldDelimiterCharacter char(1) -- any whitespace character
 AS
 BEGIN;
     DECLARE @CronExpressionArray TABLE
     (
         Seconds varchar(50)
         , Minutes varchar(50)
         , Hours varchar(50)
         , DayOfMonth varchar(50)
         , Month varchar(50)
         , DayOfWeek varchar(50)
         , Year varchar(50)
     );
     INSERT @CronExpressionArray
         SELECT
               [Seconds]    = [1]
             , [Minutes]    = [2]
             , [Hours]      = [3]
             , [DayOfMonth] = [4]
             , [Month]      = [5]
             , [DayOfWeek]  = [6]
             , [Year]       = [7]
         FROM
         (
             SELECT ds.ItemNumber, ds.Item
             FROM dbo.DelimitedSplit8K(@CronExpression, @FieldDelimiterCharacter) ds
         ) pSrc
         PIVOT
         (
             MAX(pSrc.Item)
             FOR pSrc.ItemNumber IN
                 ([1], [2], [3], [4], [5], [6], [7])
         ) pvt
     ;
     SELECT * FROM @CronExpressionArray;
 END;

DelimitedSplit8K UDF摘自文章：http://www.sqlservercentral.com/articles/Tally+Table/72993/

CREATE FUNCTION [dbo].[DelimitedSplit8K]
--===== Define I/O parameters
        (@pString VARCHAR(8000), @pDelimiter CHAR(1))
--WARNING!!! DO NOT USE MAX DATA-TYPES HERE!  IT WILL KILL PERFORMANCE!
RETURNS TABLE WITH SCHEMABINDING AS
 RETURN
--===== "Inline" CTE Driven "Tally Table" produces values from 1 up to 10,000...
     -- enough to cover VARCHAR(8000)
  WITH E1(N) AS (
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL
                 SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1 UNION ALL SELECT 1
                ),                          --10E+1 or 10 rows
       E2(N) AS (SELECT 1 FROM E1 a, E1 b), --10E+2 or 100 rows
       E4(N) AS (SELECT 1 FROM E2 a, E2 b), --10E+4 or 10,000 rows max
 cteTally(N) AS (--==== This provides the "base" CTE and limits the number of rows right up front
                     -- for both a performance gain and prevention of accidental "overruns"
                 SELECT TOP (ISNULL(DATALENGTH(@pString),0)) ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) FROM E4
                ),
cteStart(N1) AS (--==== This returns N+1 (starting position of each "element" just once for each delimiter)
                 SELECT 1 UNION ALL
                 SELECT t.N+1 FROM cteTally t WHERE SUBSTRING(@pString,t.N,1) = @pDelimiter
                ),
cteLen(N1,L1) AS(--==== Return start and length (for use in substring)
                 SELECT s.N1,
                        ISNULL(NULLIF(CHARINDEX(@pDelimiter,@pString,s.N1),0)-s.N1,8000)
                   FROM cteStart s
                )
--===== Do the actual split. The ISNULL/NULLIF combo handles the length for the final element when no delimiter is found.
 SELECT ItemNumber = ROW_NUMBER() OVER(ORDER BY l.N1),
        Item       = SUBSTRING(@pString, l.N1, l.L1)
   FROM cteLen l
;

Answer 2

SQL Server中没有内置函数来生成基于Cron表达式的下一个日期。唯一的方法是，在C＃中实现cron exprssions并将其生成为dll，然后使用SQL Server CLR注册DLL。

Refernces： https://social.msdn.microsoft.com/Forums/en-US/3e0ebe5a-d452-4893-bcef-0a1e2520c076/convert-cron-expression-to-datetime?forum=transactsql

https://github.com/atifaziz/NCrontab/wiki/SQL-Server-Crontab

Answer 3

我需要做类似的事情，最终建立自己的tSQLcron

当前它不是基于SET的，因为它是存储过程。用法示例是

    DECLARE @out_is_cron_true BIT ;

    EXEC tSQLcron.usp_is_date_in_cron_period
      @cron_expression =  N'* 0/15 * * * *' -- nvarchar(100)
    , @validate_date = '2020-01-01 13:15:00' -- datetime
    , @out_is_cron_true = @out_is_cron_true OUTPUT -- bit

    IF (@out_is_cron_true = 1 )
    BEGIN
      PRINT 'DO SOMETHING';
    END

在SQL服务器上使用T-SQL将CRON表达到下一个DateTime

3 个答案: