what is difference between foreign key and reference key
- 3 Answers
- 40612 Views
- AZTEC, Infosys, I also Faced
- E-Mail Answers
Answer Posted / suresh kumar
Hi, i give the definitions with easy understand exapmles
A primary key is used to uniquely identify each row in a
table. It can either be part of the actual record itself,
or it can be an artificial field (one that has nothing to
do with the actual record).
A primary key can consist of one or more fields on a table.
When multiple fields are used as a primary key, they are
called a composite key.
EX:If we take EMP table, Empno is the primary key and in
DEPT table, Deptno is the primary keys
A foreign key is a field (or fields) that points to the
primary key of another table.
The purpose of the foreign key is to ensure referential
integrity of the data.
In other words, only values that are supposed to appear in
the database are permitted
EX:In EMP table Deptno field is the foreign key because it
pointing to the Deptno in DEPT table
A Reference key is a field (or fields) that points to the
primary key of the same table
EX:In EMP table Mgr field is the Reference key because it
pointing to the Empno field in the same table
| Is This Answer Correct ? | 64 Yes | 12 No |
Post New Answer View All Answers
How to use group functions in the select clause using oracle?
What is a sub query? Describe its types?
What are the ways tablespaces can be managed and how do they differ?
How can I create database in oracle?
Explain rename?
How to calculate date and time differences in oracle?
Why do I get unexpected characters from 8-bit character sets in weblogic jdriver for oracle?
How to run queries on external tables?
Is primary key indexed by default in oracle?
Why is oracle so popular?
What is recycle bin in Oracle?
Which dictionary tables and/or views would you look at to diagnose a locking issue?
Explain the difference between a procedure and a function?
What is Trigger in Oracle?
What is materialized view in Oracle?
