Update a row or insert if don´t exist

[Francisco Morales]

Hello, I am trying to insert a rown if dont exist on the table or update it if
exits, i am trying with this code, but it doent works.

UPDATE productosdet set pro_id = '1' WHERE pro_id = '1'
ELSE INSERT INTO productosdet (productosdet_id, posicion_id, pro_id,
seccion_id, parent_id) values ('', '', '', 20, 1)

Anybody knows how can I do it ??

thanks a lot.