You may want to remove a foreign key constraint, but retain the underlying
HG index. A non-unique HG index can provide query
performance improvement, but may be expensive to build.
Enter an ALTER TABLE DROP FOREIGN
KEY statement. See the
ALTER INDEX statement in
Reference: Statements and Options.
Note: ALTER TABLE DROP
FOREIGN KEY CONSTRAINT does not remove the automatically created
nonunique HG index. You cannot drop a primary key if associated
foreign keys remain. To remove such an index, drop it explicitly after issuing
ALTER TABLE DROP FOREIGN KEY.