How to select records in mysql based from array of category id?

Question

I have a table where the table has a category field is array value LIKE :

|-----------------------------------|
|post_id  |   name   |  category_id |
-------------------------------------
|1        |  test1   |  1,2,45      |
|2        |  test2   |  2,7         |
|3        |  test3   |  7,13,56     |
|-----------------------------------|

From drop down select box if i select CATEGORY ID 2. i should get the result of TWO ROWS. because post_id 1 and 2 have 2 in category_id. i don't know how to do query for it. i struggled a lot. please help me out. Thanks in advance.

Answer 1

If posts can be in multiple categories, then you should reconsider the use of arrays in the category_id field, and instead use a post/category reference table, with a structure such as:

id  postId  catId

This way, you can get all posts in category 2 by (lets call this reference table 'PostCats'):

SELECT postId FROM PostCats WHERE catId=2

Answer 2

There is a simple way to sort this out. You can change the datatype of category_id to SET and using something like this:

SELECT * FROM table WHERE FIND_IN_SET('2', category_id);

Read more: FIND_IN_SET

Also look at flauntster' answer for the most appropriate way to do it.