Outer join of more than two tables
30. March 2009 05:46
Multi-table
joins have the following requirements:
-
Only two tables may be joined
at a time
-
Each Join must have an
associated
-
On clause placement must
associate the two tables being joined
Example
Select information.customer_id
customer_name,
custom_adress
from
customer_information information right outer join
campaign_new_year
campaign
on
information.customer_id = campaign.customer_id
left
outer
join job j
on
campaign.customer_id = j.customer_id
The placement
on the ON clause in the select is important. The rules are:
-
The first On clause (from
left to right) is evaluated first
-
AN On clause applies to
immediately preceding operations
When
defining 3 or more tables in outer join operations you must consider the
results of each separated join operation as a derived or temporary table
Example:
Select *
from
(Select information.customer_id
customer_name,
custom_adress
from
customer_information information right outer join
campaign_new_year
campaign
on information.customer_id =
campaign.customer_id) result
left
outer join job j
on
result.customer_id = j.customer_id) a
Email 
11/4/2011 12:02:32 AM
It`s much easier following your example
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