Oracle FAQ | Your Portal to the Oracle Knowledge Grid |
Home -> Community -> Usenet -> c.d.o.server -> Re: foreign key?
>>
No. A foreign key must always refer to the primary key of the parent
table.
Tim
<<
Not exactly correct...check out Oracle's documentation on definition of
referenced key...it could be a unique key instead of a primary key...
FOREIGN KEY (Referential) Integrity Constraints Different tables in a relational database can be related by common columns, and the rules that govern the relationship of the columns must be maintained. Referential integrity rules guarantee that these relationships are preserved.
Several terms are associated with referential integrity constraints:
foreign key
The column or set of columns included in the definition of the referential
integrity constraint that reference a referenced key (see the following).
referenced key
The unique key or primary key of the same or different table that is
referenced by a foreign key.
dependent or child table
The table that includes the foreign key. Therefore, it is the table that is
dependent on the values present in the referenced unique or primary key.
referenced or parent table
The table that is referenced by the child table's foreign key. It is this
table's referenced key that determines whether specific inserts or updates are
allowed in the child table.
A referential integrity constraint requires that for each row of a table, the value in the foreign key matches a value in a parent key.
Paul in VT Received on Tue Nov 30 1999 - 14:54:46 CST