Relational Database Design and Implementation by Harrington Jan L

Author:Harrington, Jan L. [Harrington, Jan L.]
Language: eng
Format: azw3
ISBN: 9780128499023
Publisher: Elsevier Science
Published: 2016-04-14T16:00:00+00:00

Joins Over All Columns with the Same Name

When the primary key and foreign key columns you are joining have the same name and you want to use all matching columns in the join condition, all you need to do is indicate that you want to join the tables, using the following general syntax:

The query we used as an example in the preceding section could therefore be written as

Note: Because the default is a natural equi-join, you will obtain the same result if you simply use JOIN instead of NATURAL JOIN. In fact, we rarely use the word NATURAL in queries.

The SQL command processor identifies all columns in the two tables that have the same name and automatically performs the join over those columns.

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