Question : MAke auto-increment column NOT primary key??

Hello all,

Imagine an online survey page.  A user returns to the page every day to answer the same questions.  The purpose is to track how their answers change from day to day.

They are stored in a mysal database in a table with columns:

record_id, user_id, answer_1, answer_2, ..., answer_n

When I run a report on that table, I want to select by user_id to collect all the records for user-x.  Therefore, I want the user-Id column to be the Primary Key for the table.   To ensure unique record id's, I want to make the record_id column auto_increment.

BUT, when I do that, I get an error message from mysql that an auto_increment column MUST be the Primary Key.

Is there a way to do what I want to do?

Thanks.

Answer : MAke auto-increment column NOT primary key??

You can make a column auto-increment that is not a primary key:

mysql> create table test_pk (
    -> id int auto_increment not null,
    -> userid int primary key,
    -> UNIQUE KEY (id));
Query OK, 0 rows affected (0.25 sec)

That being said, I still don't see the justification here for doing so.  Putting a primary key index on user_id will prevent a user from submitting multiple records.  It would be far better to leave the id column a primary key and create a UNIQUE index on the field (or more likely, combination of fields) that must truly be unique.