Right now, I have a table whose primary key is an
auto_increment field. However, I need to set the primary key as
date (to ensure that there cannot be a duplicate username with a date).
I need the
auto_increment field, however, in order to make changes to row information (adding and deleting).
What is normally done with this situation?
Just set a unique index on composite of (username, date).
ALTER TABLE `table` ADD UNIQUE INDEX `name` (`username`, `date`);
Alternatively, you can try to
ALTER TABLE `table` DROP PRIMARY KEY, ADD PRIMARY KEY(`username`,`date`);
and I think in the latter case you need those columns to be declared NOT NULL.
I know this is old question, here is how i solved the problem -
ALTER TABLE `student_info` ADD `sn` INT(3) UNIQUE NOT NULL AUTO_INCREMENT FIRST
Use something like:
CREATE TABLE users ( id INT PRIMARY KEY AUTO_INCREMENT, user VARCHAR(32) NOT NULL, thedate DATE NOT NULL, UNIQUE(user,thedate) );
If you already have the table, and just want to add a unique constraint on user+thedate, run
ALTER TABLE users ADD UNIQUE KEY user_date_idx (user, thedate);
Change your current primary key to be a unique key instead:
ALTER TABLE table DROP PRIMARY KEY, ADD UNIQUE KEY(username,date);
The auto_increment will function normally after that without any problems. You should also place a unique key on the auto_increment field as well, to use for your row handling:
ALTER TABLE table ADD UNIQUE KEY(id);