>>>Now I get the tablename from tcategory and I would like to update the
>>>record in the right table.
>>Your suggestion is a viable way. It does not seem to be possible
>>without a statement?
>
>I don't think I understand, in order to do an update, I always use an
>UPDATE statement, in order to select I always use a SELECT statement,
>I'd even say I use a COMMIT statement to commit my transactions. So what
>exactly do you mean with STATEMENT?
>I would like to update the table without a text-execute-statement. In
>this community I have learned that a execute statement 'insert into '
>|| :tablename || . is slower than an real statement. You know what I
>mean?

Ah, OK! I can think of two other options. The obvious is:

EXECUTE BLOCK(ID INTEGER, STATE VARCHAR(55)
AS
DECLARE VARIABLE S VARCHAR(255);
BEGIN
SELECT C.TABLE
FROM CATEGORIES C
JOIN MEMBERS M ON C.CATEGORY = M.CATEGORY
WHERE M.ID = :ID
INTO :S;
IF (S = 'TCOMPRESSOR') THEN
BEGIN
UPDATE TCOMPRESSOR SET STATE = :STATE
WHERE ID = :ID;
END
IF (S = 'TVALVE') THEN
BEGIN
UPDATE TVALVE SET STATE = :STATE
WHERE ID = :ID;
END
END;

The other one is to merge TCOMPRESSOR and TVALVE into one table (at least for the STATE field, possibly for others or all fields), and then consider having VIEWs to make it appear to the user that this field is part of the same table as other fields specific to TCompressor or TValve.

HTH,
Set