Database Reference
In-Depth Information
visible to everyone once committed by end users using the
COMMIT command.
What is the difference between Joining Tables & Linking
Tables?
Like I said before, all the joins techniques we have learnt before
viz., Outer Join, Equijoin etc. are at the query level and can be
implemented on tables having Primary/Foreign Key relationship
or not. Implementing Primary/Foreign key relationship between
two or more tables is also known as implementing Referential
Integrity (RI) constraint between those two or more tables.
Figure 2-18: Difference between Joining and Linking. Joining is at the
query level whereas linking is a physical link between tables. Joins
statements can be executed on tables having Referential Integrity
constraint or not. The word “Join” should not be confused with as I if
you are joining the two tables permanently.
The reason of bringing this topic up is, most beginners often get
confused when they read about joins and then primary key and
foreign key. They think that joins statements are only executed
on tables linked through primary and foreign key relationship but
it's not true. The word “joins” sometimes gives the feeling as if
Search WWH ::
Custom Search