Trigger help.

Hello,

        I am having difficulties setting up a simple trigger. What i want to do is this: after a insert on a table, select 2 different attributes, add them together and insert the result into a third addribute. I dont want to do a row level trigger because it doesnt make sense to have to operate on all the rows, just the most recent. The basic problem i encountered was how to select the proper row. I tried to impliment a statement level, after insert trigger and recieved this error:

	ROR at line 1:
	ORA-04082: NEW or OLD references not allowed in table level triggers

i have never heard of a "table level trigger" and cant find reference to it anywhere. (pretty much typical for my oracle experiences). In another attempt, i get this error:

	insert into test(test_first, test_second) values(4, 3)
	  *
	ERROR at line 1:
	ORA-04091: table MADIGAN.TEST is mutating, trigger/function may not see it
	ORA-06512: at "MADIGAN.PLEASE_WORK", line 7
	ORA-04088: error during execution of trigger 'MADIGAN.PLEASE_WORK'

This time i have no idea what 'mutating' means. (i suspect it means that the table is threatening to turn into the incredible hulk.)

Any help would be appreciated... (please respond by e-mail as well) Thanks.

--
tj madigan
e-mail: madigan_at_mscs.mu.edu
http://studsys.mscs.mu.edu/~madigan