sql - SQL - 根据表中行中其他字段的计数更新字段

Question

我有一个表 [applicants]，其中包含以下字段：

1) MemberID 2) 尝试

我的一些尝试是NULL。

对于表中 MemberID 计数为 1 的行，我想将尝试字段更新为 0。

任何帮助表示赞赏。

Answer 1

一般方法是

update applicants set
    Attempts = 0
where
    MemberID in (select t.MemberID from applicants as t group by t.MemberID having count(*) = 1) and 
    Attempts is null -- if you need it

在 sql server 中，您可以执行以下操作：

with cte as (
    select *, count(*) over(partition by MemberID) as cnt
    from applicants
)
update cte set
   Attempts = 0
where cnt = 1 and Attempts is null

Answer 2

UPDATE applicants
SET Attempts = 0
WHERE MemberID IN
     (SELECT MemberID FROM applicants GROUP BY MemberID HAVING COUNT(MemberID)=1)
  AND Attempts IS NULL