Natural Join

Natural Join

• It is a join technique which compares the common attributes of the tables to join the tables.
• We have to check for the common attributes in the tables well before executing the join query.
• NATURAL JOIN is the keyword used in the query to perform join.
• Natural join cause problems when new columns are added or columns are renamed or more than one set of common attributes are available. Hence, Natural join is not recommended.

Example:

SELECT * FROM Employee NATURAL JOIN Course_Registration;

The result generated by the above query is slightly different in structure from that of Equi-join. See the post on Equi-join for table instances STUDENT and COURSE_REGISTRATION and to compare the result with Natural join. The result of the above SQL query is given in Table 1;

RegNo	SName	Gen	Phone	Courses
R1	Sundar	M	9898786756	Database
R2	Ram	M	9897786776	Database
R3	Karthik	M	8798987867	Data Structures
R4	John	M	7898886756	Multimedia

 Table 1

*********

Go to Equi-join in SQL page

Go to Multiple choice questions in SQL/Relational algebra page