Question

我的表格看起来像这样：

mysql> select id, name from wp_bp_groups limit 5;
+----+-----------------------------------------+
| id | name                                    |
+----+-----------------------------------------+
|  3 | Some Group Here                         |
| 11 | Another Group Here                      |
| 29 | Groupy Groupy Groupy Group              |
| 39 | Some Other Other Group Goes Here        |
|  7 | Yep, Here's a Test Group                |
+----+-----------------------------------------+
5 rows in set (0.02 sec)

mysql> select group_id, user_id from wp_bp_groups_members limit 5;
+----------+---------+
| group_id | user_id |
+----------+---------+
|       17 |      71 |
|       24 |     209 |
|       22 |     175 |
|       17 |     200 |
|       17 |     102 |
+----------+---------+

最终，我想得到一个列出组中所有成员的数组，所以我有一个SQL查询加入它们，如下所示：

SELECT wp_bp_groups.name, wp_bp_groups_members.user_id FROM wp_bp_groups LEFT JOIN wp_bp_groups_members ON wp_bp_groups.id = wp_bp_groups_members.group_id;

其中输出的内容如下：

mysql> SELECT wp_bp_groups.name, wp_bp_groups_members.user_id from wp_bp_groups left join wp_bp_groups_members on wp_bp_groups.id = wp_bp_groups_members.group_id limit 5;
+------------------+---------+
| name             | user_id |
+------------------+---------+
| Test Group       |       1 |
| Test Group       |     206 |
| Test Group       |      24 |
| Test Group       |      47 |
| Test Group       |      52 |
+------------------+---------+
5 rows in set (0.02 sec)

但理想情况下，我希望能够返回更像这样的内容：

name: Test Group
user_ids: 1, 206, 24, 47, 52

有办法吗？

Answer 1

在MySQL中，您可以使用函数group_concat，它将连接每个组中的所有元素。所以你必须对结果进行分组。如果您想获得所有用户ID，可以查询

SELECT wp_bp_groups.name, GROUP_CONCAT(wp_bp_groups_members.user_id) as user_ids FROM wp_bp_groups LEFT JOIN wp_bp_groups_members ON wp_bp_groups.id = wp_bp_groups_members.group_id group by wp_bp_groups.name;

应该以

结果

+------------------+----------------------+
| name             | user_ids             |
+------------------+----------------------+
| Test Group       |       1,206,24,47,52 |
+------------------+----------------------+

在SQL中，有没有办法将表转换为列表？

1 个答案: