while循环中的Tsql联合

Tsql union in while loop(while循环中的Tsql联合)

问题描述

我试图在更改 where 子句中的某些值时将同一个表与其自身联合在一起.我的问题是循环之间的联合.我不能使用表变量，因为架构太复杂，无法每次都手动编写.临时表似乎是要走的路，但我不知道如何让它工作和正确的语法.

I am trying to union the same table together with itself while changing some value in the where clause. The problem i have is with the union between the loops. I can not use a table variable since the schema is too complicated to write by hand each time. Temp tables seem to be the way to go but I do not know how to get it to work and the correct syntax.

我想要实现的伪代码:

DECLARE @var int, #tempTable
SET @var = someValue

WHILE expressionIncludingVar
  #tempTable = SELECT *
  FROM someTable
  WHERE column = @var
  UNION ALL #tempTable

  SET @var = someChangeToVar

RETRUN #tempTable

查询的结果应该是 #tempTable 因此奇怪的RETURN #tempTable".

The result of the query should be #tempTable hence the weird "RETURN #tempTable".

提前致谢.

另一个硬编码示例:我正在尝试对这样的东西进行硬编码:

Another hardcoded example: I am trying to unhardcode something like this:

 SELECT someAggregateColumns
 FROM table
 WHERE someDateColumn > @date and < someDateColumn < DATEADD(month, 2, @date)
 GROUP BY someColumn
 UNION ALL
 SELECT someAggregateColumns
 FROM table
 WHERE someDateColumn > DATEADD(month, 1, @date) and and < someDateColumn < DATEADD(month, 1, DATEADD(month, 3, @date))
 GROUP BY someColumn
 SELECT someAggregateColumns
 FROM table
 WHERE someDateColumn = DATEADD(month, 2, @date) DATEADD(month, 1, DATEADD(month, 4, @date))
 GROUP BY someColumn
 UNION ALL 
 ....etc

推荐答案

也许递归 CTE 适合您.

Maybe Recursive CTE works for you.

你可以试试这个.

DECLARE @MyTable TABLE(ID INT, ColumnA VARCHAR(10), ColumnB VARCHAR(10))
INSERT INTO @MyTable VALUES
(1,'A', '10'), 
(2,'B', '11'),
(3,'C', '12'),
(4,'D', '13'),
(5,'E', '14'),
(6,'F', '15'),
(7,'H', '16')

DECLARE @var INT = 4

;WITH CTE AS (
    SELECT * FROM @MyTable WHERE ID = @var
    UNION ALL 
    SELECT T.* FROM CTE INNER JOIN @MyTable T ON CTE.ID - 1 = T.ID 
)
SELECT * INTO #tempTable FROM CTE

SELECT * FROM #tempTable

DROP TABLE #tempTable

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