how i would perform something like, adding a new non-nullable column to an existing table, would be:
adding that column in first step as nullable, otherwise you will not get the rdbms to modify the table, because it will violate the not null constraint.
updating the new column to the data you want it to have
UPDATE event e SET e.ticketing_information_id = (SELECT `id` FROM `ticketing_information` WHERE id = e.id)
Your update needs to tell the inner select, which row it is currently updating, so you are able to filter only the data of that particular row in the inner select.
modifying the column to be not null