I\'m trying to update the column visited to give it the value 1. I use MySQL workbench, and I\'m writing the statement in the SQL editor from inside the workben
It looks like your MySql session has the safe-updates option set. This means that you can't update or delete records without specifying a key (ex. primary key) in the where clause.
Try:
SET SQL_SAFE_UPDATES = 0;
Or you can modify your query to follow the rule (use primary key in where clause).