Question

Question:

Is it possible to have enforce multiple column constraint when creating a table in mySQL, as opposed to later including it by altering the table?

Background:

I have noticed almost all answers to the question “how to create a multi column unique constraint in mySQL” involve using ALTER on a table, here are 2 examples from here alone:

• ON DUPLICATE KEY: multi-column unique constraint
• Use multiple columns as unique identifier for mysql

The only examples I find which create multi column constraint when creating the table are for different flavors of sql:

• How to place unique contraint on multiple column
• How to do multiple column unique-constraint in ormlite ( SQLite )
• microsoft sql example

Is there a way to create the constraint when creating the table as I find it is cleaner that way?

Answer 1

CREATE TABLE mytable (
   field1 int,
   field2 int,
   field3 int,
   UNIQUE KEY (field1, field2, field3)
);