Re: I'm sorry, another dumb question about Triggers

Originally posted by Tk
> I promise to keep my questions to a minimum after this... Pardon my
> ignorance but I'm going thru the trigger examples in the Oracle
> 8i PL/SQL
> book. p. 270 has the following trigger:
> --------
> CREATE OR REPLACE TRIGGER GenerateStudentID
> BEFORE INSERT OR UPDATE ON students
> FOR EACH ROW
> BEGIN
> /* Fill in the ID field of students with the next value from
> student_sequence. Since ID is a column in students, :new.ID
> is a valid reference. */
> SELECT student_sequence.NEXTVAL
> INTO :new.ID
> FROM dual;
> END GenerateStudentID;
> --------
> I understand clearly what this is doing. However, I'm
> dumbfounded as to
> "why" they have this also called on an UPDATE statement?
> When I issue the following update:
>
> update students set major = 'Computer Science' where id = 10020;
>
> The actual "id" gets changed from 10020 to 10021 due to the
> trigger logic.
> Pardon my complete ignorance and "moronity" (if such a word exists)
> but does
> not that violate referential integrity (since ID is the primary
> key) and is
> it not considered a bad thing to update the primary key of an
> existing row?
> I wonder if they meant to have just: BEFORE INSERT ON students
> rather than
> BEFORE INSERT OR UPDATE ON students
>
> In all of my past/present jobs, once a row has a primary key
> associated with
> it, that primary key "value" never gets changed.
>
> thanks...

Pretty bad example. Who is the author?

Regards
/Rauf Sarwar

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