Create table fails with Foreign Key Constraint is incorrectly Formed

I have received this message many times while using 3rd party tools to create tables and then constrain against existing tables. It's either one of two things:

• The int columns have different sizes
• The int columns have different flags (sans AUTO_INCREMENT)

As an example, I created a table with a tool that somehow created a column as INT(10) instead of the expected INT(11). Even though I just chose INT when creating both, it was messed up - never tracked down why.

Long story short, it's generally best to explicitly state the INT size when creating a table.

In your case, the following should work:

create table users (id int(11) not null auto_increment, username varchar(255) NOT NULL, password varchar(255) NOT NULL, active int NOT NULL, PRIMARY KEY (id))ENGINE=InnoDB COLLATE=utf8_unicode_ci;create table athing (id int(11) not null auto_increment, name varchar(255) not null, status varchar(255) not null, created_by_user_id int(11) not null, PRIMARY KEY (id), CONSTRAINT athing_fk1 FOREIGN KEY (created_by_user_id) REFERENCES users (id)) ENGINE=InnoDB COLLATE=utf8_unicode_ci;