How do I specify unique constraint for multiple columns in MySQL?

Question

I have a table:

table votes (
    id,
    user,
    email,
    address,
    primary key(id),
);

Now I want to make the columns user

Answer 1

For PostgreSQL... It didn't work for me with index; it gave me an error, so I did this:

alter table table_name
add unique(column_name_1,column_name_2);

PostgreSQL gave unique index its own name. I guess you can change the name of index in the options for the table, if it is needed to be changed...