database - Mysql Unique record 2 columns -

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i making application inserts users mysql database.

i know can make column value unique, want combination of 2 columns in record unique.

for example:

id   firstname   lastname    creationdate -----------------------------------------  1   john        doe         (today)

what want achieve can enter record :

 2, john, deo, (today)

but cannot enter:

2, john, doe, (today)

what sql statement can use make combination of multiple columns unique?

use below query

alter table persons add constraint pk_personid primary key (firstname,lastname)

http://www.w3schools.com/sql/sql_primarykey.asp


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