Re: dbcoltype() , char and nchar

LacaK wrote:
> 
> Only for explanation:
> In FreePascal there are different Database Field Types
> TStringField and TWideStringField, so my attempt was map
> char, varchar to TStringField
> nchar, nvarchar to TWideStringField (see 
> http://docwiki.embarcadero.com/VCL/en/DB.TWideStringField )
> (text to TMemoField, ntext to TWideMemoField)

I understand what you want to do.  Unfortunately it will be quite
difficult with db-lib, because FreeTDS intentionally conceals the server
column definition.  It was a design decision -- maybe not the right one!
-- but it's very deep in the library.  

As soon as UCS-2 data arrive from the server, they are immediately
converted to the client's encoding.  The UCS-2 form is discarded.[1]  To
provide UCS-2 data to FreePascall, you'll have to re-convert!  

Getting db-lib to report the server's type and size wouldn't be
particularly hard.  The TDSCOLUMN structure has a nested on_server
structure with exactly that information.  That structure could be
harmlessly added to the DBCOL structure filled by dbcolinfo().  I think if
you look at dbcolinfo() and dbcoltype(), you'll see what to do.  Look at
tds_set_column_type() too.  

HTH.  

--jkl

[1] This was my design many years ago, and I now think it was the wrong
choice.  Converting to the client's charset is a matter of *binding*, and
binding should be handled as late as possible.  dbbind() is where the
conversion should happen, and dbdata() should return the original UCS-2
data as delivered by the server.