SQL串联行查询 [英] SQL concatenate rows query

问题描述

说我们有一张桌子

table posts
+---------+-----------+--------------------------------+
| postId  | title     | status    | bodyText           |
+---------+-----------+--------------------------------+
|   1     | Hello!    | deleted   | A deleted post!    |
|   2     | Hello 2!  | deleted   | Another one!       |
|   3     | New 1     | new       | A new one!         |
|   4     | New 2     | new       | A new one again!   |

我们可以通过SQL发出单个查询，而不必在后端代码中循环进行联接，从而在SQL中检索跨行的字段的连接吗?

Can we, in SQL, retrieve a concatenation of a field across rows, by issuing a single query, not having to do the join up in a loop in our back-end code?

类似

select title from posts group by status ;

应该给出类似的结果

+---------+--------------------+
| deleted | Hello!, Hello 2!   |
| new     | New 1, New 2       |

推荐答案

如果使用MySQL，则可以使用

If you use MySQL then you can use GROUP_CONCAT:

SELECT status, GROUP_CONCAT(title)
FROM posts
GROUP BY status

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