No two rows in the table can have the same value for the defined column set. The system uses a unique primary or secondary index to enforce this constraint.
Only one primary key can be specified per table. To specify candidate primary keys for referential integrity relationships with other tables, use the UNIQUE definition clause.
You cannot specify a PRIMARY KEY constraint for a QITS column (see “QITS_column_name” earlier in this table).
The system implicitly creates a unique index on any column set specified as PRIMARY KEY if it is not also defined to be the primary index for the table.