Understanding this trigger

Question

Hi ,
What does this trigger do ?
CREATE OR REPLACE TRIGGER "LR_INS_02" BEFORE INSERT ON "TT"."LR" REFERENCING OLD AS OLD NEW AS NEW FOR EACH ROW
when (NEW.R_ID IS NOT NULL)
BEGIN
SELECT E_TYPE INTO :NEW.ETYPE
FROM R
WHERE R_ID = :NEW.R_ID;
END;
is it updating the field call ETYPE in TT table ? or NEW.Etype is a bind variable ?
kindly advise
tks & rdgs

Answer 1

The table LR has a denormalized column called ETYPE. Denormalized means that it is stored in table R, but also redundantly in table LR. Possibly for performance reasons.
Now when you insert a record in table LR and you specify the column R_ID with a not null value, this trigger automatically looksup the corresponding ETYPE in table R and fills column ETYPE in table LR.
For an explanation about :new values in triggers, please refer to the Oracle documentation. And, by the way, TT is not a table but a schema name.
Hope this helps.
Regards,
Rob.