to avoid infinite recursion in such scenarios.

</para>

<para>

If a foreign key constraint specifies referential actions (that

is, cascading updates or deletes), those actions are performed via

ordinary SQL update or delete commands on the referencing table.

In particular, any triggers that exist on the referencing table

will be fired for those changes. If such a trigger modifies or

blocks the effect of one of these commands, the end result could

be to break referential integrity. It is the trigger programmer's

responsibility to avoid that.

</para>

<para>

<indexterm>

<primary>trigger</primary>