Question

假设我有一个包含两列的表，一个是int和一个布尔值。我需要在int列（阈值）中找到最小值，超过该值，布尔列中的所有值都为TRUE。如何构建此查询？

例如：

level  | detection
-----------------
5      | False
6      | True
7      | False
8      | True
9      | True
10     | True

此特定场景应返回8级。

Answer 1

试试这个，

Declare @Table table (level int,detection varchar(25))
insert into @Table values
(5,'False')
,(6,'True')
,(7,'False')
,(8,'True')
,(9,'True')
,(10,'True')

SELECT min(LEVEL) AS Threshold
FROM @Table
WHERE LEVEL > (
        SELECT max(LEVEL)
        FROM @Table
        WHERE detection = 'False'
        )

Answer 2

一种可能的方式（online demo）。

WITH T
     AS (SELECT *,
                Prev = LEAD([detection]) OVER (ORDER BY [level] DESC),
                CumeRowCount = SUM(1) OVER (ORDER BY [level] DESC 
                                            ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW),
                CumeTrueCount = SUM(CASE WHEN [detection] = 'True' THEN 1 END) OVER 
                                           (ORDER BY [level] DESC 
                                           ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)
         FROM   YourTable)
SELECT TOP 1 [level]
FROM   T
WHERE  CumeRowCount = CumeTrueCount /*All preceding and current rows must be true*/
       AND Prev <> [detection]      /* Next row not true*/
ORDER  BY [level] DESC

用于查找最小值的SQL查询，在该值之上，另一列中的所有值都满足某些条件

2 个答案: