Problem with SQL query [Inner join and multiple selects]

Question

here is my query:

SELECT * FROM 
   (SELECT messages.*, 
   users.* 
   FROM `afo_messages` as messages 
   INNER JOIN `key_users` as users ON messages.user_id = users.id 
   WHERE messages.category_id=5 
   ORDER BY messages.id DESC LIMIT 30) ilv 
ORDER BY messages.id ASC

Error is "#1060 - Duplicate column name 'id'".

Table afo_messages columns:

id | user_id | category_id | parent_id | message | create_date | update_date | status

Table key_users columns:

id | name | email | phone | pwd | active | role | invite_id | download_link | date

What I'm doing wrong?

Thanx!

Answer 1

Pretty sure that when you run the inner query, the result set has two columns called ID (on from messages, one from users); you're then running a query on that subquery, and the parser doesn't understand it.

Try:

SELECT * FROM 
(SELECT messages.id as message_id,
       messages.user_id, 
       ....all other columns from messages

       users.id as real_user_id, 
       users.name, 
       ..... all other columns from users
FROM `afo_messages` as messages 
INNER JOIN `key_users` as users ON messages.user_id = users.id 
WHERE messages.category_id=5 
ORDER BY messages.id DESC LIMIT 30) ilv 
ORDER BY message_id ASC

Answer 2

You are selecting two columns called ID without aliasing one. Do you really need ALL of the columns from both tables. This is generally bad practice. You would probably be better off specifying exactly which columns you want and aliasing one of the ID s. For example:

SELECT * FROM 
   (SELECT messages.ID,  
    messages.message, 
    users.id as UserId, --aliasing this column to UserId
    users.name, 
    users.email
   FROM `afo_messages` as messages 
   INNER JOIN `key_users` as users ON messages.user_id = users.id 
   WHERE messages.category_id=5 
   ORDER BY messages.id DESC LIMIT 30) ilv 
ORDER BY messages.id ASC

Answer 3

Your internal query says SELECT messages.*, users.*... and both afo_messages and key_users have an id field. Pick one, or alias them.

Answer 4

You have two id columns, one in each table. You need to not use SELECT * and alias at least one of them to give it a distinct name.

SELECT * FROM (SELECT messages.id AS messageid, ...

Answer 5

It doesn't match the error message, but shouldn't your final ORDER BY be by ilv.id?

In the context of your outer query, no table named "message" was ever referenced.