Most tables contain a column that is a foreign key. This column enables users to join columns and combine tables. When combined, the tables can be referenced as if they were a single table.
For example, one of the columns of table ATTRIBUTE is a foreign key called PARENT_ENTITY_ID. This column can be joined, or matched, with the ID column of table ENTITY_TYPE to discover the parent entity type to which the attribute belongs.
Joining the foreign key column, PARENT_ENTITY_ID with the target column, ID, in the ENTITY_TYPE table shows that the attribute Governor belongs to the entity type State.
For more information, see the illustration in Identification.
The following join technique described and illustrated by the table is used extensively to select related objects from the Public Interface.
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