Hi,

I have this table definition:
CREATE TABLE CONSUMPTION
(
ID KEYS NOT NULL,
QUANTITY Integer DEFAULT 0,
UNITPRICE Numeric(18,2) DEFAULT 0,
CONSUMEDVALUE Numeric(18,2) DEFAULT 0,
REMARKS Varchar(50) COLLATE UNICODE_CI_AI,
CONSUMED Timestamp,
MATURITYFIRST Integer,
MATURITYBEST Integer,
MATURITYPAST Integer,
TRANSFER_ID Bigint,
FK_CBBOTTLEID Bigint,
FK_CELLARBOOK_ID KEYS,
FK_RATING_ID KEYS,
FK_CELLAR_ID KEYS,
FK_REASON_ID KEYS,
CREATED_AT Timestamp,
UPDATED_AT Timestamp,
CREATED_BY KEYS,
UPDATED_BY KEYS,
CONSTRAINT PK_CONSUMPTION PRIMARY KEY (ID)
)

CREATE TRIGGER CONSUMPTION_CONSVAL FOR CONSUMPTION
ACTIVE AFTER INSERT OR UPDATE POSITION 0
AS
BEGIN
/* enter trigger code here */
new.CONSUMEDVALUE = new.UNITPRICE * new.QUANTITY;
END

When I try to update manually (e.g. using FlameRobin or IBExpert) the
column "CONSUMEDVALUE" or when I try to create the above trigger I get
this error:

SQL Message : -151
This column cannot be updated because it is derived from an SQL function
or expression.

Engine Code : 335544359
Engine Message :
attempted update of read-only column

What am I doing wrong?

Werner