If Statement and selecting a row

Using MYSQL.

Trying to write an IF Statement.

Table name: Erreur Columns names: Company, ID, Published, Type, Erreur_type, etc

select * from erreur
where Erreur_type IS NOT NULL
IF Erreur_type = 1 Then SET Published = NULL
ELSE Erreur_type = 2 Then SET Type = 'Ordinaire'
ELSE Erreur_type = 3 Then SET TYPE = 'Extraordinaire'
END IF;

My question is, do I need: -To select a row or I can use this code on multiple rows at ones?