Trigger Overhead

It is important to remember that, by necessity, triggers add overhead to the DML statements to which they apply. The actual amount of overhead will depend upon the nature of the trigger, butas all MySQL triggers execute FOR EACH ROWthe overhead can rapidly accumulate for statements that process large numbers of rows. You should therefore avoid placing any expensive SQL statements or procedural code in triggers.

We will look at an example of trigger overhead in Chapter 22.