In Oracle PL/SQL, control structures are used to manage the flow of execution in a program. These structures allow developers to dictate the order in which statements are executed based on certain conditions or loops. The primary control structures in PL/SQL include conditional statements IF statement, IF-THEN-ELSE, loops (FOR, WHILE, and LOOP), and branching statements (GOTO).
The IF-THEN statement of PL/SQL language has the same structure as the others equivalent procedural languages. The IF-THEN statement allows selective execution of actions based on the fulfillment of certain conditions.
If you want to execute a certain section of code only if a condition is true, you can use an IF-THEN statement.
IF condition THEN -- statements END IF;
You can also use an IF-THEN-ELSIF statement to check multiple conditions.
IF condition_1 THEN -- statement_1 ELSIF condition_2 THEN -- statement_2 END IF;
If you want to execute a certain section of code only if a condition is NOT true, you can use an IF-THEN-ELSE statement.
IF condition_1 THEN -- statement_1 ELSIF condition_2 THEN -- statement_2 ELSE -- statement_3 END IF;
CASE statements are used to perform conditional branching based on the value of an expression. You can use the CASE statement to select one of several alternative sections of code to execute.
CASE expression WHEN condition_1 THEN statement_1; WHEN condition_2 THEN statement_2; WHEN condition_3 THEN statement_3; ELSE statement_4; END CASE;
FOR LOOP Statements
The FOR LOOP statement is used to iterate a specific number of times.
FOR counter IN start_value..end_value LOOP -- code to be executed in each iteration END LOOP;
WHILE LOOP Statements
The WHILE LOOP statement is used to create a loop that continues as long as a specified condition is true.
WHILE condition LOOP -- code to be executed in each iteration END LOOP;
The GOTO statement allows unconditional branching to a labeled statement within the same block or subprogram.
<<label_name>> GOTO label_name;
These control structures in PL/SQL provide the flexibility needed to write powerful and efficient programs by allowing developers to control the flow of execution based on different conditions and requirements. It’s important to use them judiciously to ensure code readability and maintainability.