constraining a table field -> not duplicate value, not a primary key
> How to constrain a column in my table so it can't have two or more
> similar values at a time and it isn't a primary key ?

Should I use `CHECK` or `CONSTRAINT` or ... ? what's the right way to achieve that ?

**note :** I'm using MySQL
constraining a table field -> not duplicate value, not a primary key
===

> How to constrain a column in my table so it can't have two or more
> similar values at a time and it isn't a primary key ?

Should I use `CHECK` or `CONSTRAINT` or ... ? what's the right way to achieve that ?

**note :** I'm using MySQL