mySQL - linking two columns as unique 1

[soundmind]

Hi y'all,

Is there a way to link two columns within a table to be unique?

For example, the columns in a table "users" are:
user_id(primary key, auto_increment), user_name, date

I'd like to have user_name and date linked to each other so there could be only one entry per user_name per day. Is this possible in mySQL?

Thank you!!!

 

[sleipnir214]

Don't use "date" as the name of a MySQL column. "date" is a MySQL reserved word.

If the table already exists, to add a UNIQUE index combining the user_name and user_date columns (

http://www.mysql.com/doc/en/ALTER_TABLE.html):

ALTER TABLE tablename
ADD UNIQUE indexname (user_name, user_date)


To add the UNIQUE index to a table at table creation (

http://www.mysql.com/doc/en/CREATE_TABLE.html):

CREATE TABLE tablename
(
user_id int unsigned auto_increment primary key,
user_name varchar(25) not null,
user_date date,
UNIQUE indexname (user_name, user_date)
}

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TANSTAAFL!!