Question

我有一张这样的桌子使用这些字段＆gt;＆gt;＆gt;

我希望将s-id = 1＆gt;＆gt;＆gt;＆gt;相关性值的数量更新为2

(s-id)(relevancy)
0         null
0         null
3         2
4         null
4         null
4         null
4         null
5         2
9         null

这是我的代码：

    SELECT s-id,COUNT(s-id) from ccc
    group by s-id

    update ccc set Relevancy=2 where COUNT(s-id)=1

但我认为聚合函数不能在where子句中使用，我现在应该怎么做？

Answer 1

UPDATE ccc SET Relevancy = 2 
WHERE (SELECT COUNT(*) FROM ccc c2 WHERE c2.[s-id] = ccc.[s-id])  = 1

Demo （最后一行的Relevancy更新为2，因为9是唯一的）

另一种选择是CTE使用COUNT(*)OVER：

WITH CTE AS
(
    SELECT [s-id], Relevancy,
           CNT = COUNT(*) OVER (PARTITION BY [s-id])
    FROM CCC
)
UPDATE CTE SET Relevancy = 2 WHERE CNT = 1

Demo

Answer 2

update   dbo.YourTable
set      Relevancy = 2
where    [s-id] in
         (
         select  [s-id]
         from    dbo.YourTable
         where   Relevancy <> 2
         group by
                 [s-id]
         having  count(*) = 1
         )

在where子句中使用聚合函数进行sql更新

2 个答案: