On Tue, Jul 15, 2003 at 08:53:12AM -0700, Alan Mead wrote: > > --- James Mills <[EMAIL PROTECTED]> wrote: > > On Tue, Jul 15, 2003 at 08:35:44AM -0700, Alan Mead wrote: > > > > > > --- James Mills <[EMAIL PROTECTED]> wrote: > > > > > > > My program relies on the fact that some fields (which are > > string > > > > types) > > > > are null. I'm not sure what to say next so I'll leave it at > > that :P > > > > > > If your database never contains an empty string, then your > > program > > > can rely on the empty strings you retrieve being NULL values in > > the > > > database. > > > > This case is true and the database will never contain empty strings > > only > > NULL values. The program has strict ways of doing this, unless of > > course > > you modify the databases externally, then bam (you're right as per > > below)... > > So if you do nothing, your program will work unless someone accesses > the database externally (or there is a bug in whatever code ensures > against inserting empty strings). You need to decide how likely and > bad that is.
Well the only bad thing is that it returns data where there should be no data. ie: '""' instead of the expected '', causing the program to treat '""' as if it were a real string. James > > But maybe there is a simple work-around. Surely you can execute SQL > select statements using SQLite, right? If so, then you can exploit > the fact that SQL itself is well aware of the distinction between > empty strings and NULL's to check for this error condition. > > If you're checking one table called MYTABLE with a key called IDX and > a couple fields to check are ADDRESS1 and ADDRESS2 then you would > execute this select: > > select IDX from MYTABLE where ADDRESS1='' or ADDRESS2='' > > If you get no results, then there is no error condition (you can > safely assume empty strings are NULL's). If you get any results, > then you know which records need to be fixed. > > You could execute this query at the start of your application's run. > Or you could run it periodically (e.g., nightly) and email yourself > the results. > > -Alan > > __________________________________ > Do you Yahoo!? > SBC Yahoo! DSL - Now only $29.95 per month! > http://sbc.yahoo.com > > _______________________________________________ > fpc-pascal maillist - [EMAIL PROTECTED] > http://lists.freepascal.org/mailman/listinfo/fpc-pascal -- - - James Mills Zero Defect Software Engineers Group - ZDSEG _______________________________________________ fpc-pascal maillist - [EMAIL PROTECTED] http://lists.freepascal.org/mailman/listinfo/fpc-pascal
