将MySQL字段uid设置为auto_increment

Question

For some reason i keep getting the following error when i try to set my uid as auto_increment. I am using phpMyAdmin.

Error

SQL query:

ALTER TABLE `ITEMS` ADD `uid` INT( 2 ) NOT NULL AUTO_INCREMENT FIRST ,
ADD `name` VARCHAR( 100 ) NOT NULL AFTER `uid` ,
ADD `status` VARCHAR( 100 ) NOT NULL AFTER `name`

MySQL said: Documentation
#1075 - Incorrect table definition; there can be only one auto column and it must be defined as a key 

I had a few other tables in my database that originally had index as auto_increment but I changed all those columns to uid varchar. But now I am adding a table named ITEMS and I want uid to be the "master" key that I can use as a reference point to all my other tables.

Answer 1

You need to add the PRIMARY KEY constraint to your new column. BTW, this may mean removing that constraint from any old column that was originally AUTO_INCREMENT.

Answer 2

You're not adding a table, but changing it. New specification comes in conflict with what exists in the schema, you can do show table and post it here for us to see.