Advanced Database Management System - Tutorials and Notes: Natural Join

Sunday, 23 March 2014

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

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Go to Equi-join in SQL page

Go to Multiple choice questions in SQL/Relational algebra page


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