Data Modeling - Foreign Key Constraint
1 - About
A Foreign Key (also known as as a foreign key constraint) is:
- a column
- or combination of columns
used to establish and enforce a relationship between data in two tables.
Usually the foreign key is coupled with the primary key of the other table.
2 - Articles Related
3 - Example
An Foreign Key example of a database (with the scott schema from Oracle).
Consider a part of the EMP (Employe) table.
The column DPTNO from the EMP table refer to the column DEPTNO from the table DEPT (Department) below :
For each DPTNO in the table EMP, you must have a DPTNO in the table DEPT. We say then that :
- the column DPTNO from the table EMP is a foreign key.
- and then that the column DEPTNO is a primary key.
If it's not true, there is NO referential integrity.