On 13/03/2013 11:46, Charl Roux wrote:
> Thanks for the response.
>
> 1.
> I have used the following line to determine if the table does exist in
> the database:
> if( tableList->IndexOf("queryBackup") < 0 )
> errorCode = frmDataModule->eyeConnection->ExecuteDirect(SQL);
Please don't top-post: it makes the discussion hard to follow. Also,
please reply to the list rather than directly to me.
I know Delphi rather than C++ Builder, so I may be missing something,
but let's look at your code anyway:
void __fastcall TfrmMain::FormCreate(TObject *Sender)
{
int errorCode;
TStringList *tableList = new TStringList;
frmDataModule->eyeConnection->GetTableNames(tableList);
// create queryBackup table if does not exist
AnsiString SQL = "CREATE TABLE queryBackup( queryName VARCHAR(30)
PRIMARY KEY,query VARCHAR(10000))";
if( tableList->IndexOf("queryBackup") < 0 )
errorCode = frmDataModule->eyeConnection->ExecuteDirect(SQL);
}
I'm guessing that the GetTableNames method is supposed to populate the
TStringList with a list of available tables - is that right? If so, have
you established that tableList actually contains anything after the call
to GetTableNames?
Another point is that PostgreSQL identifiers are folded to lower-case
automatically - so maybe IndexOf("querybackup") will return something
different to IndexOf("queryBackup").
> This worked perfectly with MySQL, now with PostgreSQL it is as if the line
> if( tableList->IndexOf("queryBackup") < 0 )
> is ignored or not understood by C++Builder
Try the "...if not exists..." qualifier I mentioned in my last email;
using that, you can just issue the "create table" command without having
to check in your code whether the table exists.
> 2.
> I am using VARCHAR(30), to use as little space as possible, and allowing
> up to 30 characters. With MySQL the alternative was CHAR(30) which uses
> a constant amount of space. So with TEXT type, will it only use the
> amount of space required, according to the amount of characters the user
> entered?
Yes. In fact, there's no real reason, space- or performance-wise, to use
varchar(n) unless you really need the limit on the length of the string.
You can read all about it here:
http://www.postgresql.org/docs/9.2/static/datatype-character.html
As I said before, the only thing to watch (in my Delphi experience
anyway) is that if you're binding DB columns to data-aware controls,
TEXT gets mapped to a memo type rather than to a string.
HTH,
Ray.
--
Raymond O'Donnell :: Galway :: Ireland
rod@xxxxxx
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