Best practice to update a row if exists otherwise insert [duplicate]

Question

This question already has an answer here:

• Insert into a MySQL table or update if exists 11 answers

I want to know more efficient way to update a row in table, if row not exists it must be inserted.

My query is

UPDATE MyGuests SET lastname='Doe' WHERE id=2

When this query is run and there is no row with id=2, a row must be inserted like

INSERT INTO MyGuests (lastname, id)
VALUES ('Doe', 2)

Note:

1. My primary intention is to update the row

2. I don't want primary key change when updating a row.

Answer 1

Assuming that id is your Primary/Unique Key, you can use INSERT..ON DUPLICATE KEY UPDATE :

INSERT INTO MyGuests (id, lastname) VALUES (2, 'Doe')
  ON DUPLICATE KEY UPDATE lastname = 'Doe'

Answer 2

You can refer this way:

UPDATE MyGuests SET lastname='Doe' WHERE id=2
IF ROW_COUNT()=0
    INSERT INTO MyGuests (lastname, id) VALUES ('Doe',2)