Question

i have table category the format is like this

|id|parent_id|name|  
|1 |0        |sport|  
|2 |0        |music|
|3 |1        |Stadium|
|4 |1        |Golf| 
|5 |2        |Theater|
|6 |2        |Cinema|

Desc

parent_id = 0 is Main category

parent_id != 0 is Sub category and the main Category is Parent_id

and this is the table users

|id|name|category_id|
|1 |andrea|6        |
|2 |Michael | 5     |
|3 |Gorchuf | 1     |

The Problem

selection Category that is Include on Users table and showing only main category example the goal will be like this

|id|name|total|
|1 |sport |1  |
|2 |music |2  |

i’m try with this query

SELECT C.id C.name, count( U.category_id ) AS total
FROM categories C
LEFT JOIN users U ON ( U.category_id = C.id )
GROUP BY C.id
LIMIT 0 , 30

but the result is include sub category and main category

|id|name|total|
|1 |cinema |1 |
|2 |theater|1 |
|3 |sport  |1 |

How can I filter that only main category?

Answer 1

QUERY:

SQLFiddleExample

SELECT c.id, c.name,
(SELECT  count(u.id)
 FROM users u
  LEFT JOIN categories c1
    ON u.category_id = c1.id
  WHERE CASE WHEN c1.parent_id = 0 
             THEN c1.id
             ELSE c1.parent_id 
        END = c.id) AS total
FROM categories c
WHERE c.parent_id = 0
GROUP BY c.id

Result:

| ID |  NAME | TOTAL |
----------------------
|  1 | sport |     1 |
|  2 | music |     2 |