Beginning Oracle Database 11g Administration From Novice to Professional

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CHAPTER 2 SQL AND PL/SQL
Storing programs in the database has many advantages. Special PL/SQL programs
called triggers can be executed whenever a user performs a specified action. This gives
us the ability to enforce business rules, control access to data, and keep records of who
accessed the data and how it changed. Storing sequences of commands in the database
greatly reduces the amount of communication between client and server and thus
improves efficiency. Also, PL/SQL functions can be utilized in SQL statements; this
increases the power and flexibility of SQL.
Much Ado About Suppliers
This section provides SQL solutions for the queries listed in the “Exercises” section of
Chapter 1. Other solutions exist; remember that most SQL statements can be written
in various ways. In this chapter’s “Exercises” section, you will be asked to rewrite these
statements without using query factoring and without using the operator.
Parts That Are Supplied by All Suppliers
The answer to this problem looks similar to the answer to the problem List the suppliers
who supply all parts. All we have to do is to interchange the roles of suppliers and parts,
as shown in Listing 2-22.
Listing 2-22. Parts That Are Supplied by All Suppliers