Hi Dmitry,
Thank you very much for answer!
Yes now I see it :

"The <update source> of each <set clause> is effectively evaluated
for each row of T before any row of T is updated.
For each subject row, a candidate new row is constructed by copying
the subject row and updating it as
specified by each <set clause> by applying the General Rules of
Subclause 14.12, "<set clause list>"."

-Laco.

>
> lacakus wrote:
> >
> > I encounter following situation (problem?):
> >
> > update table1
> > set column1=value1, column2=column1
> > where ...
> >
> > When I run this statement in Firebird (also in MySQL), evaluation

and

> > assignment of each <set clause> is done sequentialy, so at the

end of

> > statement column2 equals to value1
>
> Accordingly to the SQL specification, this is wrong.
>
> > When I run this statement in MS SQL Server, right sides of each

<set

> > clause> are evaluated first and assignment is done after, so at

the end

> > of statement column2 equals to original "OLD.column1"
>
> This is correct.
>
> Starting with v2.5 Beta, FB will behave correctly by default, but

you

> can revert back to the legacy mode via firebird.conf.
>
>
> Dmitry
>