PL/SQL Conditional Statements

Decision-Making is an important part for most of the computer programs. It helps to develop the program code logically. For correct decision making, PL/SQL provides us with the Conditional Statements. These Conditional Statements helps us to develop a proper algorithm and a logical program.

Decision-making programs or structures require that the developer mentions conditions to be evaluated or tested by the program, along with statements to be executed if the condition is determined to be true, and also, statements which need to be executed if the condition is determined to be false.

PL/SQL Conditional Statements

PL/SQL IF-THEN Statement

The IF statement accompanies a condition with a sequence of statements enclosed by END IF and THEN. If the condition is true, the statements get executed and if the condition is FALSE or NULL then it does nothing. The control passes to the succeeding statements in any case.

Syntax


Example

Output

PL/SQL IF-THEN Statement

PL/SQL IF-THEN-ELSE Statement

This statement uses an IF condition along with an ELSE block. If the condition is TRUE, then the statements in the IF block will be executed and if the condition is NULL or FALSE, then the alternative sequence of statements gets executed that is written in ELSE Block. This statement ensures that at least one of the sequence of statements is executed. 

Syntax


Example


Output

PL/SQL IF-THEN-ELSE Statement

PL/SQL IF-THEN-ELSIF Statement

There may arise a situation wherein you need to choose one of the several alternatives. If the first condition is FALSE or NULL, the ELSIF block tests another condition. An IF statement can have multiple ELSIF blocks and the final ELSE clause is optional. Conditions are evaluated from top to bottom one by one. If any condition is true, the sequence of statements in that particular block is executed and control passes to the next statement. If all the succeeding conditions are FALSE, the sequence in the ELSE block is executed. Consider the following example.

Syntax

PL/SQL CASE Statement

Like the IF-THEN-ELSEIF statement, the CASE statement selects one sequence of statements to execute from several alternatives.

The CASE statement uses a selector whereas IF-THEN and IF-THEN-ELSIF statements use Boolean expressions. A selector is an expression developed by the programmer whose value is used to select one of several alternatives mentioned in the program under different Cases.

The CASE statement is efficient compared to IF statements and hence if the IF-THEN-ELSE programs become lengthy, it is recommended to use CASE statements.

The CASE statement begins with the keyword CASE and is followed by a selector rather than an expression. The selector expression is evaluated only once.The value it yields can be a BFILE, PL/SQL record, BLOB, an index-by-table, an object type, a varray, or a nested table. The selector expression can also contain function calls which may be a complex one. It consists of a single variable generally. 

The ELSE clause is not mandatory to write. If you omit it, PL/SQL adds the ELSE block implicitly.

Syntax

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