What's the difference between using INDEX vs KEY in MySQL?

Question

I know how to use INDEX as in the following code. And I know how to use foreign key and primary key.

CREATE TABLE tasks ( 
  task_id INT UN         


        

Answer 1

It is mentioned as a synonym for INDEX in the 'create table' docs: MySQL 5.5 Reference Manual :: 13 SQL Statement Syntax :: 13.1 Data Definition Statements :: 13.1.17 CREATE TABLE Syntax

Nos already cited the section and linked the help for 5.1.

Like PRIMARY KEY creates a primary key and an index for you, KEY creates an index only.