Table Structure

CREATE TABLE Areas(AreaName VARCHAR(255),
                    PinCode VARCHAR(255))
                    
INSERT INTO Areas(AreaName, PinCode)VALUES
                 ('Teynampet', '6000018'), 
                 ('Ramapuram', '6000089'),
                 ('TNagar', '6000017'), 
                 ('Mylapore', '6000014'), 
                 ('Gopalapuram', '6000087')

Stored Procedure

DROP PROCEDURE IF EXISTS mp_test;
CREATE PROCEDURE mp_test(IN pArea VARCHAR(255))
   BEGIN
      SET @Query = '';
      SET @City  = '';
      SET @Query = 'SELECT PinCode FROM Areas';

      IF pArea != '' THEN
         SET @City = CONCAT(' WHERE AreaName = "', pArea, '"');
      END IF;
      
      SET @Query = CONCAT(@Query, @City);

 PREPARE stmt FROM @Query;
 
 EXECUTE stmt;
 DEALLOCATE PREPARE stmt;  
END