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Pro Oracle SQL, Second Edition by Jared Still, Riyaj Shamsudeen, Robyn Sands, Kerry Osborne, Karen Morton

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CHAPTER 11

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Semijoins and Antijoins

Semijoins and antijoins are two closely related join methods (options of join methods, actually) that the Oracle optimizer can choose to apply when retrieving information. The SQL language is designed to specify the set of data the user wishes to retrieve, but to leave the decisions regarding how to navigate to the data up to the database itself. Therefore, there is no SQL syntax to invoke a particular join method specifically. Of course, Oracle does provide the ability to give the optimizer directives via hints. In this chapter, I explain these two join optimization options, the SQL syntax that can provoke ...

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