Thanks for your reply.

I have resolved my problem. Infact, the data are not identical. I'm
working on a linux box using Firebird C API.



--- In firebird-support@yahoogroups.com, Svein Erling Tysvær
<svein.erling.tysvaer@...> wrote:

>
> If the phone fields are identical (NULLs aren't identical), then
> records should be returned. Try
>
> select 'x'||a.PHONE||'x' from tb1 a
>
> and
>
> select 'x'||a.PHONE||'x' from tb2 b
>
> just to eliminate that it is something stupid like one of the

tables

> containing spaces. I must admit that I've never tried using

different

> character sets, maybe that could influence Firebird? But I guess

phone

> contains numbers and they are pretty similar in most languages.
>
> Your SQL seems OK to be, I would of course recommend using SQL-92

and

> not SQL-89 and rewrite your query to
> select a.PHONE,a.content from tb1 a join tb2 b on a.phone=b.phone;
> but your sql should work.
>
> Set
>
> --- In firebird-support@yahoogroups.com, "tailuo2002" wrote:
> > The sql below doesn't return any row:
> >
> > select a.PHONE,a.content from tb1 a,tb2 b where a.phone=b.phone;
> >
> > But tb1 and tb2 has the same PHONE structure and many PHONE data

are

> > same.
> >
> >
> > tb1 structure:
> > ...
> > phone varchar(18) nullable
> > ...
> >
> > tb2 structure:
> > ...
> > phone varchar(18) nullable
> > ...
> >
> > Thank you.
>