Oracle sub-table foreign keys do not need to be indexed

In general, the foreign key of the Oracle sub-table needs to be indexed,

If no index is added to the foreign key, modifying the parent table will lock the child table.

1. Update the primary key of the parent table, and the child table will be locked.

2. delete a row from the parent table. The entire sub-table will be locked.

3. merged to the parent table. The child table is locked. (9i, 10g is the case, 11g is not ).

If the following three conditions are met, you do not need to create an index with the foreign key

1. Data is not deleted from the parent table.

2. The primary key of the parent table is not updated.

3. No parent table is associated with the child table