[fpc-pascal]SQLite and NULL Strings...

[Michael Van Canneyt]

On Mon, 14 Jul 2003, James Mills wrote:

> On Mon, Jul 14, 2003 at 09:59:17AM +0200, Michael Van Canneyt wrote:
> >
> >
> > On Mon, 14 Jul 2003, James Mills wrote:
> >
> > > Hi,
> > >
> > > This is a very weird behaviour I've found of either SQLite, or the Unit.
> > > I'm not sure... I have been discussing this same problem on the SQLite
> > > mailing list but without success there, so perhaps someone here might
> > > know...
> > >
> > > I have attached a test database, which contains 1 database entry, null
> > > strings are inserted using NULL... Check the database schema yourself.
> > >
> > > The problem therein lies in the fact that test3.pas returns "" for the
> > > query: SELECT channelNotice FROM channels WHERE channel LIKE '#ProLogiTech';
> > > It should return a null string as it does in test2.pas and in the sqlite
> > > shell program.
> >
> > The problem is that an implicity conversion from Nil to empty string is
> > done. You cannot solve this as long as stringlists are used to contain
> > the data. (ok, you could set 'Null' as the string, but that is sloppy)
>
> "is done." in what ? The SQLite library or TStringList ?

sqlite.

>
> >
> > You'd need to have (as a minimum) an array of TField records:
> >   TField = Record
> >     IsNull : Boolean;
> >     Value : String;
> >   end;
> >
> > But this will require major changes, so I suggest trying to find or
> > implement a TDataset descendent for SQLIte, this will solve most of
> > your problems at once.
>
> How major would the changes be ? Otherwise I'll try and search for a
> TDataset descendent ? Couldn't I write a descendent myself ? (I've kinda
> of done something similar in creating a TDatabase descendant..., but it
> doesn't solve my problem)

Implementing a TDataset descendent is not easy, it'll take you at least
a week (conservative estimate).

Michael.