PL/SQL includes conditional statements, and one of the fundamental conditional constructs is the IF-THEN statement. The IF-THEN statement in PL/SQL is used for conditional execution of a block of code. It allows you to specify a condition, and if that condition evaluates to true, then a specified block of code is executed.


Here’s a basic syntax for the IF-THEN statement:

IF condition THEN
   -- statements to be executed if the condition is true

Let’s break down the components of the IF-THEN statement:

condition: This is the expression that evaluates to either true or false. If the condition is true, the statements inside the THEN block are executed. If the condition is false, the execution continues with the statements after the END IF.

THEN: This keyword marks the beginning of the block of code that should be executed if the condition is true.

END IF: This keyword marks the end of the IF-THEN block. It signifies that the conditional block of code has ended, and the execution continues with the statements following the END IF.


Here’s a simple example of using IF-THEN in PL/SQL:

   x NUMBER := 10;
   -- Check if x is greater than 5
   IF x > 5 THEN
      DBMS_OUTPUT.PUT_LINE('x is greater than 5');
   END IF;

In this example, if the value of x is greater than 5, the message ‘x is greater than 5’ will be displayed.

You can also use the ELSIF and ELSE clauses to extend the IF-THEN statement for more complex conditional logic. Here’s an example:

   y NUMBER := 3;
   -- Check the value of y
   IF y > 5 THEN
      DBMS_OUTPUT.PUT_LINE('y is greater than 5');
   ELSIF y = 5 THEN
      DBMS_OUTPUT.PUT_LINE('y is equal to 5');
      DBMS_OUTPUT.PUT_LINE('y is less than 5');
   END IF;

In this case, the program checks the value of y and prints different messages based on the condition. If y is greater than 5, it prints one message; if y is equal to 5, it prints another message; otherwise, it prints a third message.

The IF-THEN statement is a fundamental building block for creating conditional logic in PL/SQL, allowing developers to control the flow of execution based on specific conditions.