The UNIQUE constraint

The syntax when using unique in [[The CREATE statement]]:

CREATE TABLE table_name (
column_name data_type,
...
UNIQUE KEY (column_name)
);

The syntax when using unique in [[The ALTER statement]]:

ALTER TABLE table_name 
ADD UNIQUE KEY (column_name);

The syntax to drop a unique constraint on a column using [[The DROP statement]]:

ALTER TABLE table_name
DROP INDEX column_name;