plpgsql if statement

if condition then
  statements;
else
  alternative-statements;
END if;

        
            
        
     DO $$
DECLARE
  a integer := 10;
  b integer := 20;
BEGIN 
  IF a > b THEN
	RAISE NOTICE 'a is greater than b';
  END IF;

  IF a < b THEN
	RAISE NOTICE 'a is less than b';
  END IF;

  IF a = b THEN
	RAISE NOTICE 'a is equal to b';
  END IF;
END $$;