Question

I’m trying to auto increment the art_id in the table below based on the art_userid, Is this possible without writing any extra php code? The gen_id has to remain and cannot be removed. I’m using Mysql and Php

CREATE TABLE `articles` (
        `gen_id` INT(10) NULL AUTO_INCREMENT,
        `art_id` TINYINT(3) NULL DEFAULT '0',
        `art_userid` INT(10) NULL DEFAULT '0',
        `art_title` VARCHAR(150) NULL DEFAULT NULL,
        PRIMARY KEY (`gen_id`)

So in the end, if user 1 posted an article, his art_id would be 1. The next one he posts would have the id 2.

But if user 2 posted and article, his art_id would be 1 again. The next one he posts would have the id 2. Not the continuation of the 1st users art_id.

gen_id | art_id | art_userid | art_title
-----------------------------------------
1         1        1           Title A
2         2        1           Title B
3         1        2           Title A
4         2        2           Title B
5         3        1           Title A

Answer 1

Well, I kinda solved it, but with one less column. The engine type needs to be MyIsam for this. Then do a create like this:

CREATE TABLE `articles` (
    `art_id` INT(10) NOT NULL AUTO_INCREMENT,
    `art_userid` INT(10) NOT NULL DEFAULT '0',
    PRIMARY KEY (`art_userid`, `art_id`)
)
COLLATE='utf8_general_ci'
ENGINE=MyISAM;

Then when you insert art_userid, you’ll get a unique value for art_id starting from 1 for each user.