In Oracle, there is an option to disable a primary key constraint with the cascade option in the ALTER TABLE command. This option disables the primary key constraint as well as the foreign key constraints of all the tables that reference this table. But when you enable the primary key constraint then the foreign key constraints of all those tables will not be enabled because there is no option like we have in the disable (ie, the cascade option). I think that the following query will do the trick:
select 'Alter table ' || table_name || ' enable constraint ' || constraint_name || ';' from user_constraints where constraint_type='R' and r_constraint_name=(select constraint_name from user_constraints where constraint_type='P' and table_name='the parent table name goes here');
Kim R. writes: If you disable a unique or primary key constraint that is using a unique index, Oracle drops the unique index. That can be a gotcha if one isn't aware of it.
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This was first published in March 2003