Re: MySQL ERROR: Can't update table SQL trigger

[Peter Brawley]

As the manual makes clear, a Trigger cannot invoke Update or Insert on the table for which the Trigger is defined.

For that table, a Trigger can only change values in the row(s) for which it's defined by referencing OLD.column_name and setting NEW.column_name values (otherwise a Trigger could invoke infinite loops).

So, in a Trigger on an appointments table, an Update Trigger fired by a change in the starting time needs only to SET NEW values for appt duration or appt-ending time.