Question

I have a table that stores “records” and already has primary key.

Table A
=======
id (INT) PK auto_increments
project_id (INT)
record_text (TEXT)

This table stores “records” for all of my projects. It is desirable to have a secondary key that auto increments for the projects.

Example: If project 1 had id’s of (1,5,8,9). It would be desirable to store them and present them to the user as (1,2,3,4).

I do not have the ability to use TRANSACTIONS and I’m having trouble thinking of a way of doing this without causing concurrency issues.

Hopefully I got my problem across clearly. Thank you in advance for the help.

Edit (Example):
Assuming the structure:
id, project_id, record text
1 1 testing
2 1 testing
3 2 testing
4 1 testing

My ID’s for project 1 would 1,2,4. But I’m looking for a way to store and display them for project 1 as 1,2,3

Answer 1

I’m not sure what I was thinking, too late in the day probably, but I was able to achieve this by adding a column to the table:

id, pid, project_id, record_text

pid being the numbering system for the project.

The INSERT:

INSERT INTO A (id, pid, project_id, record_text) 
VALUES (
    NULL, 
    (SELECT COALESCE(new_id, 0) + 1 FROM (SELECT MAX(new_id) AS new_id FROM atest WHERE project_id = 1) AS x),
    1,
    'some text'
);

Now as my project changes my pid, id based off the project, auto-increments too:

id    pid    project_id    record_text
1     1      1             testing 123
2     2      1             testing 123
3     1      2             testing 123
4     3      1             testing 123

Thank you all for your input and I apologize for my poor description of the problem.