Question

SELECT enquiry.*,
      (SELECT comm
       from comments
       where enquiry.id = comments.enquiryId
       order by time DESC
      ) as comm
FROM enquiry
where id='110' AND cmpId='3'

当我想通过删除限制来执行多行时，它说＆＃34;子查询执行多行＆＃34; 请帮忙

Answer 1

您的子查询称为标量子查询，这意味着它必须有一列，最多一行。一种简单的方法是使用JOIN：

将结果放在多行中

SELECT e.*, c.comments
FROM enquiry e JOIN
     comments c
     ON e.id = c.enquiryId
where e.id = 110 AND e.cmpId = 3;

Answer 2

或者您可以将子查询放在from子句中（如下所示），这与连接条件类似。

SELECT enquiry.*, comm.comm
FROM enquiry,
      (SELECT comm
       from comments
       where enquiry.id = comments.enquiryId
       order by time DESC
      ) as comm
where id='110' AND cmpId='3'

Answer 3

作为询问与...之间的关系评论是1到多（如图所示）您需要添加GROUP_CONCAT（）函数以对所有注释进行分组，如下所示：

SELECT enquiry.*,
      (SELECT GROUP_CONCAT(comm)
       from comments
       where enquiry.id = comments.enquiryId
       order by time DESC
      ) as comm
FROM enquiry
where id='110' AND cmpId='3'

子查询执行多行，我的查询不同

3 个答案: