i am using Like in group concat & i want to get all modules attached to client even if it does not match to LIKE, i know that that i can do that with HAVING but i don’t want to use HAVING, any solution with WHERE or in join condition ?
Any suggestions on how to get my expected result??
These are some basic tables and the query i tried along with results i get and the result i really wanted
Tables
x
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 |
+-------------------------+
Query:
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
Results:
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 |
+------------------------------------------------------+
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Answer
This is possible without HAVING
by using 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;
But this is less efficient, and more verbose so offers no advantage whatsoever. I expect your reasons for using HAVING
are largely unfounded, and the approach I would personally take is with a conditional count in the HAVING
clause:
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;