Question

I am trying to use nested query to avoid having to issue two different queries. My nested query is as shown below;

INSERT INTO roles (
   _id, 
   user_id,
   user_role)
VALUES (
((SELECT _id FROM roles ORDER BY _id DESC LIMIT 1)+1), '454', 'USER')

But when I execute I get;

Lookup Error – MySQL Database Error: You can’t specify target table
‘roles’ for update in FROM clause

Is there any work around to this query or I simply can’t do insert and select on the same table?

Answer 1

If you’re using MySQL >= 4.0.14, you can use INSERT ... SELECT:

INSERT INTO roles (
  _id, 
 user_id,
 user_role
)
SELECT _id + 1, '454', 'USER' FROM roles ORDER BY _id DESC LIMIT 1

However, it looks as though you probably just want to make your _id column AUTO_INCREMENT and then don’t provide any value for it. MySQL will do the rest:

ALTER TABLE roles MODIFY _id INT AUTO_INCREMENT;
INSERT INTO roles (user_id, user_role) VALUES (454, 'USER');