PL/SQL - IF-THEN Statement

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It is the simplest form of the IF control statement, frequently used in decision-making and changing the control flow of the program execution.

The IF statement associates a condition with a sequence of statements enclosed by the keywords THEN and END IF. If the condition is TRUE, the statements get executed, and if the condition is FALSE or NULL, then the IF statement does nothing.

Syntax

Syntax for IF-THEN statement is −

IF condition THEN  
   S; 
END IF; 

Where condition is a Boolean or relational condition and S is a simple or compound statement. Following is an example of the IF-THEN statement −

IF (a <= 20) THEN
   c:= c+1;
END IF;

If the Boolean expression condition evaluates to true, then the block of code inside the if statement will be executed. If the Boolean expression evaluates to false, then the first set of code after the end of the if statement (after the closing end if) will be executed.

Flow Diagram

Example 1

Let us try an example that will help you understand the concept −

DECLARE 
   a number(2) := 10; 
BEGIN 
   a:= 10; 
  -- check the boolean condition using if statement  
   IF( a < 20 ) THEN 
      -- if condition is true then print the following   
      dbms_output.put_line('a is less than 20 ' ); 
   END IF; 
   dbms_output.put_line('value of a is : ' || a); 
END; 
/

When the above code is executed at the SQL prompt, it produces the following result −

a is less than 20 
value of a is : 10  

PL/SQL procedure successfully completed. 

Example 2

Consider we have a table and few records in the table as we had created in PL/SQL Variable Types

DECLARE 
   c_id customers.id%type := 1; 
   c_sal  customers.salary%type; 
BEGIN 
   SELECT  salary  
   INTO  c_sal 
   FROM customers 
   WHERE id = c_id; 
   IF (c_sal <= 2000) THEN 
      UPDATE customers  
      SET salary =  salary + 1000 
         WHERE id = c_id; 
      dbms_output.put_line ('Salary updated'); 
   END IF; 
END; 
/

When the above code is executed at the SQL prompt, it produces the following result −

Salary updated  

PL/SQL procedure successfully completed.