SQL JOIN多个ID

Question

First Table

|product_name   |   category_ids  |
|---------------------------------|
|- apple        |   1, 2          |
|- extra_apple  |   1, 3          |

---

Second Table

|category_id  |   category_name   |
|---------------------------------|
|- 1          |   fruit           |
|- 2          |   cheap           |  
|- 3          |   expensive       |

---

How can I join this, so I get something like this

|     product_name  |     category_names   |
--------------------------------------------
|     apple         |     fruit, cheap     |
|     extra_apple   |     fruit, expensive |

Answer 1

To make it right, add another table:

product_categories table
------------------------
product_id
category_id

It contains one record for each category a product has.