[fpc-pascal]SQLite and NULL Strings...
Michael Van Canneyt
michael.vancanneyt at wisa.be
Mon Jul 14 14:26:28 CEST 2003
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 ?
> > 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).
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