On Mon, 14 Jul 2003, James Mills wrote:
> On Mon, Jul 14, 2003 at 02:26:28PM +0200, Michael Van Canneyt wrote: > > > > > > 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. > > But you said "You cannot solve this as long as stringlists are used to > contain the data." This made me think it was a behaviour of TStringList > ... If it truely is a behaviour of SQLite, I'll get them to change it. The problem is that there is no way to distinguish between a 'null' and an empty string once it is converted to a string. The information is simply lost. > > > > > > > > > > > > > > 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). > > Why is this a hard thing to do ? Give me some ideas here, you might be > conservative, but I don't muck around :) Because TDataset is not an easy subject. You need to implement a lot of calls in a correct and predefined way. Michael. _______________________________________________ fpc-pascal maillist - [EMAIL PROTECTED] http://lists.freepascal.org/mailman/listinfo/fpc-pascal
