Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

An Alternative INNER JOIN
Let’s do a déjà vu thing and look back at the first INNER JOIN we did in this chapter:
USE AdventureWorks2008
SELECT *
FROM Person.Person
INNER JOIN HumanResources.Employee
ON Person.Person.BusinessEntityID = HumanResources.Employee.BusinessEntityID
This got us approximately 290 rows back. Instead of using the JOIN, however, let’s rewrite it using a
WHERE-clause–based join syntax. It’s actually quite easy — just eliminate the words INNER JOIN, add a
comma, and replace the ON operator with a WHERE clause:
SELECT *
FROM Person.Person, HumanResources.Employee
WHERE Person.Person.BusinessEntityID = HumanResources.Employee.BusinessEntityID
It’s a piece of cake and it yields us the same 290 rows we got with the other syntax.
This syntax is supported by virtually all major SQL systems (Oracle, DB2, MySQL, and so on) in the
world today, but can create some ambiguity at what point in the query processing the restriction should be
applied. It is very rare to run into such an ambiguity, but it can happen, so use the JOIN syntax for any
new queries and edit old queries to the new syntax as you are able.
An Alternative OUTER JOIN
Note that the alternative syntax for OUTER joins is only available if you tell SQL
Server you want to run in SQL Server 2000 compatibility mode (setting the compatibility
level to 80 in the ALTER DATABASE command).
The alternative syntax for OUTER JOINs works pretty much the same as the INNER JOIN, except that,
because we don’t have the LEFT or RIGHT keywords (and no OUTER or JOIN for that matter), we need
some special operators especially built for the task. These look like this:
Alternative ANSI
*= LEFT JOIN
=* RIGHT JOIN
Let’s pull up the first OUTER JOIN we did in this chapter. It made use of the pubs database and looked
something like this:
SELECT sso.SpecialOfferID, Description, DiscountPct, ProductID
FROM Sales.SpecialOffer sso
Chapter 4: JOINs
105