在mysql查询中连接表？

Question

I would like to run a query on two table "products" and "category", There are 30 record in my product table. product table has a column name category_ids varchar(255),which storing the ids of category in the format like(10,11,12,130,..) for each record of products table. In sort a product can be many categories. category table having a column name parent_id which is the parent category of that category.

I want to list the record with all category of that product.

For example look at one record of the products table having id = 7.

    product_Id = 7,
    category_ids = '213,215,216',
    product_name = 'Ponds', 
    .....

Means product ponds has three category = category.id = 213, category.id = 215 and category.id = 216.

I want to list here all three records of ponds like in this format :=

product_Id | product_name | category_name | parent_category_name
   7           ponds          cream              chemical
   7           ponds          medicine           chemical
   7           ponds          powder             Ayurvedic    

I am trying with this query :-

select
p.id as product_id,
p.product_name,
child.name as category_name,
parent.name as parent_category_name
from category child 
left join products p on child.id in(p.category_ids) 
left join category parent on parent.id = child.parentid and parent.parentid = 0
where p.id = 7  

The above query getting only one record not all three records as above.

What condition and joining in this query will be applied to get result as above described.

Sorry for spending your valuable time.

Any suggestions and ideas would be greatly appreciated.

Thanks a lot.

Answer 1

Try to change ON condition -

LEFT JOIN products p ON child.id IN(p.category_ids) 

->

LEFT JOIN products p ON FIND_IN_SET(child.id, p.category_ids)

...because:

SELECT 1 IN ('1,2,3') find_1, 2 IN ('1,2,3') find_2;
+--------+--------+
| find_1 | find_2 |
+--------+--------+
|      1 |      0 | -- 0 !
+--------+--------+


SELECT FIND_IN_SET(1, '1,2,3') find_1, FIND_IN_SET(2, '1,2,3') find_2;
+--------+--------+
| find_1 | find_2 |
+--------+--------+
|      1 |      2 |
+--------+--------+

---

GROUP_CONCAT function.

example:

SELECT p.product_Id, p.product_name, GROUP_CONCAT(c.category) FROM products p
  JOIN category c
    ON FIND_IN_SET(child.id, p.product_Id)
GROUP BY p.product_Id;