LIKE group_concat with where 子句

Question

我在 group concat 中使用 Like & 我想将所有模块附加到客户端，即使它与 LIKE 不匹配，我知道我可以用 HAVING 做到这一点，但我不想使用 HAVING , 任何具有 WHERE 或连接条件的解决方案 ?

关于如何获得我的预期结果有什么建议吗？？

这些是一些基本表和我尝试的查询以及我得到的结果和我真正想要的结果

表

Client
+--------------------+
| id      |  name    |
+--------------------+
| 1       | client1  |
| 2       | client2  |
| 3       | client3  |
| 4       | client4  |
+--------------------+

Module
+--------------------+
| id      |  name    |
+--------------------+
| 1       | module1  |
| 2       | module2  |
| 3       | module3  |
| 4       | module4  |
+--------------------+

Client_Module
+-------------------------+
| client_id  | module_id  |
+-------------------------+
| 1          | 1          |
| 1          | 3          |
| 2          | 1          |
| 2          | 2          |
| 2          | 4          |
| 3          | 2          |
| 4          | 1          |
| 4          | 2          |
| 4          | 3          |
| 4          | 4          |
+-------------------------+

查询：

SELECT     client.id, client.name, GROUP_CONCAT(module.name) AS modules
FROM       client
LEFT JOIN  client_module ON client_module.client_id = client.id
LEFT JOIN  module ON module.id = client_module.module.id
WHERE      module.name LIKE '%module1%'
group by client.id

结果：

Received
+--------------------------------------------------+
| id     | name     | modules                      |
+--------------------------------------------------+
| 1      | client1  | module1                      |
| 2      | client2  | module1                      |
| 4      | client4  | module1                      |
+--------------------------------------------------+

Expected
+------------------------------------------------------+
| id     | name     | modules                          |
+------------------------------------------------------+
| 1      | client1  | module1,module3                  |
| 2      | client2  | module1,module2,module4          |
| 4      | client4  | module1,module2,module3,module4  |
+------------------------------------------------------+

Answer 1

这应该有效

SELECT     client.id, client.name, GROUP_CONCAT(module.name) AS modules
FROM       client
LEFT JOIN  client_module ON client_module.client_id = client.id
LEFT JOIN  module ON module.id = client_module.module.id
GROUP BY   client.id
HAVING     modules LIKE '%module1%'

Answer 2

无需 HAVING 即可使用 EXISTS:

SELECT  c.id, c.name, GROUP_CONCAT(m.name) AS modules
FROM    client AS c
        INNER JOIN client_module AS cm
            ON cm.client_id = c.id
        INNER JOIN module AS m
            ON m.id = cm.module_id
WHERE   EXISTS
        (   SELECT  1
            FROM    client_module AS cm2
                    INNER JOIN module AS m2
                        ON m2.id = cm2.module_id
            WHERE   m2.name LIKE '%module1%' 
            AND     cm2.client_id = c.id
        )
GROUP BY  c.id, c.name;

但这效率较低，而且更冗长，因此没有任何优势。我希望您使用 HAVING 的理由在很大程度上是没有根据的，我个人会采取的方法是在 HAVING 子句中使用条件计数：

SELECT  c.id, c.name, GROUP_CONCAT(m.name) AS modules
FROM    client AS c
        INNER JOIN client_module AS cm
            ON cm.client_id = c.id
        INNER JOIN module AS m
            ON m.id = cm.module_id
GROUP BY  c.id, c.name
HAVING COUNT(CASE WHEN m.name LIKE '%module1%' THEN 1 END) > 0;

Example on db<>fiddle

LIKE group_concat with where 子句

LIKE group_concat with where clause

mysql

sql

conditional-statements