Oracle PL/SQL Programming, Third Edition

Chapter 4. Conditional and Sequential Control

This chapter describes two types of PL/SQL control statements: conditional control statements and sequential control statements. Almost every piece of code you write will require conditional control, which is the ability to direct the flow of execution through your program based on a condition. You do this with IF-THEN-ELSE and CASE statements (CASE statements are new in Oracle9i). There are also CASE expressions; while not the same as CASE statements, they can sometimes be used to eliminate the need for an IF or CASE statement altogether. Far less often, you will need to tell PL/SQL to transfer control unconditionally via the GOTO statement, or explicitly to do nothing via the NULL statement.

IF Statements

In your programs, you need to be able to implement requirements such as:

If the salary is between ten and twenty thousand, then apply a bonus of $1500. If the salary is between twenty and forty thousand, apply a bonus of $1000. If the salary is over forty thousand, give the employee a bonus of $500.

or:

If the user preference includes the toolbar, display the toolbar when the window first opens.

The IF statement allows you to design conditional logic into your programs. The IF statement comes in three flavors, as shown in the following table:

IF type	Characteristics
IF THEN END IF;	This is the simplest form of the IF statement. The condition between IF and THEN determines whether the set of statements between THEN and END IF ...