Question

我知道这张桌子，

元：

| id | comment_id | key         | value   |
|  1 |      1     | _status     | pending |  
|  2 |      2     | _comment_id |    1    |
|  3 |      2     | _status     | pending |

我想要的是从_status = pending的行中检索comment_id值，这些行没有指向自身的_comment_id =行。

更好地解释一下这个伪代码。

status = getRows( {key: _status, value: pending} );
ids = getRows( {key: _comment_id } )

what_i_want = []
foreach status as comment_status_id:
    if comment_status_id not in ids:
        what_i_want[] = status_id

这样做的最佳方式是什么？是否可以仅使用sql执行此操作？

如果该表应该返回：[2]

Answer 1

您可以使用group by和having：

执行此操作

select comment_id
from table t
group by comment_id
having sum(case when key = '_status' and value = 'pending' then 1 else 0
           end) > 0 and
       sum(case when key = '_comment_id' and value = cast(comment_id as varchar(255))
                then 1 else 0
           end) = 0;

如果您正在寻找status =“pending”，并且注释ID为和，则注释ID不会指向自身：

select comment_id
from table t
group by comment_id
having sum(case when key = '_status' and value = 'pending' then 1 else 0
           end) > 0 and
       sum(case when key = '_comment_id' then 1 else 0 end) > 0 and
       sum(case when key = '_comment_id' and value = cast(comment_id as varchar(255))
                then 1 else 0
           end) = 0;

从行unmatch中选择行ID

1 个答案: