1. Before triggers are used to validate insert/update data.
e.g. cannot have someone who is aged above 150years or negative.
e.g. can set all data values to be camelcase so that data is uniform
e.g. can be used to abstract insert statement by generating complex
inserts that use joins and the like so that inner workings of the db
becomes a "black box"- insert with 4 columns -> trigger -> insert,select with
x columns
2. After triggers can be used to backup row data in a backup table.
can also be used to update interest rates dynamically without need to
update the program code.