Re: Computed column?

Jane Mikityanskaya wrote:
>
> Working with Oracle Rdb, I was spoiled by possibility of creating
> 'computed by' columns.
> For example, creating table ' Test' I could define:
> column A integer,
> column b integer,
> column c as (a+b)/10;
> Since there is no such feature in Oracle 7.3, can someone tell me a
 work
> around for 'computed' fields?
>

> Second solution:
>
> Create table Test with column A integer, column B integer, column C
> number (n, m)
>
> Create a trigger which will insert/update in C the computed value
> (A+B)/10.
>

The following trigger returns an error (ORA - 04091) during execution:

CREATE OR REPLACE TRIGGER c_compute
 AFTER INSERT OR UPDATE OF A, B ON Test
  FOR EACH ROW
Begin
update test
 set C = Power((A+B),2)
End;

The trigger has been created without any errors (does that mean it's'compiled'?)).
Issuing the statement :

    Update Test set a = a + 0 ;
produces an error.
Could you please, tell me What I'm doing wrong?

Thanks for any help.
Jane Received on Tue Jul 22 1997 - 00:00:00 CDT