Another way to enforce uniqueness is to add a UNIQUE index rather than a PRIMARY KEY to a table. : Primary Key « Key « SQL / MySQL






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Another way to enforce uniqueness is to add a UNIQUE index rather than a PRIMARY KEY to a table.

    
mysql>
mysql> CREATE TABLE person
    -> (
    ->     last_name CHAR(20) NOT NULL,
    ->     first_name CHAR(20) NOT NULL,
    ->     address CHAR(40),
    ->     UNIQUE (last_name, first_name)
    -> );
Query OK, 0 rows affected (0.00 sec)

mysql>
mysql> drop table person;
Query OK, 0 rows affected (0.00 sec)








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