Re: Using parameters with the low level ADO API, trying to avoid the memory leaks.

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Date: Wed, 23 Feb 2005 16:16:41 +0300

> Satisfied, I changed "WHERE LineID = '1'"
> to "WHERE LineID = :LineID".

MS ADO (without ADOExpress or dbGo) passes SQL directly to OLEDB provider.
You do not say which provider you use, but most of them will not understand
parameters in for :ParamName. For most providers ? should be used:

WHERE LineID = ?

And try to use EmptyParam instead of Null.

//------------------------------------------
Regards,
Vassiliev V. V.
http://www.managed-vcl.com - using .Net objects in Delphi for Win32 +
ADO.Net
http://www.oledbdirect.com - The fastest way to access MS SQL Server,
MS Jet (Access) and Interbase (through OLEDB)

"Rich" <Arby_001@Yahoo.com> ÓÏÏÂÝÉÌ/ÓÏÏÂÝÉÌÁ × ÎÏ×ÏÓÔÑÈ ÓÌÅÄÕÀÝÅÅ:
news:421bbd1e$1@newsgroups.borland.com...
>
> This tale involves using the ADO API. We find a problem, we
> have a work around, but there is still has a challange to left
> to be met.
>
> We are using Delphi 7 SP1 & MDAC 2.7 SP2 and working with a
> Paradox table for this experiment.
>
> Several others here and I have had problems with memory leaks
> using TADOConnection and TADOCommand. My app runs 24x7 and
> I’m getting desperate.
>
> I’m now working directly with the Microsoft ADO components as
> exposed with ADOInt. Types such as CoConnection, CoCommand,
> and CoRecordSet to bypass some of Delphi's VCL wrapper overhead.
>
> I've made progress over the last couple of days getting my feet
> Wet, but I ran into a problem. I believe it has to do with the
> way that Visual Basic can call a ComObject vs. Delphi.
>
> I started with a simple SQL Update with no parameters. Each
> time I run the command, the update is reflected properly in
> the table.
>
> Satisfied, I changed "WHERE LineID = '1'"
> to "WHERE LineID = :LineID".
>
> I can populate the parameter as required, either using the
> Command.Parameters.Refresh() to create and then populate them,
> or create them individually and use
> Command.Parameters.Append(objParam) to assign them.
>
> When I run the CoCommand’s execute method, the update does not
> occur. No amount of playing with the parameter, or the data type
> makes a difference. There isn't any exception generated, just a
> big fat 0 records affected. The update just does not happen.
>
> So I tried the third alternate method of passing a variant array
> at execute time. That works.
>
> Here is the first call:
>
> RecordsAffected is an OleVariant.
> adCmdText is a constant that equals 1. It tells ADO
> that our CommandText is the literal SQL statement.
> ParamCol is a Variant, not an OleVariant.
> objParam is a CoParameter.
>
> Fails:
> ObjCmd.Execute(RecordsAffected,null,adCmdText);
>
>
>
> Works:
> ParamCol := VarArrayCreate([0, 0], VarVariant);
> ParamCol[0] := objParam; {Created earlier}
>
> ObjCmd.Execute(RecordsAffected,ParamCol,adCmdText);
>
> The VB Call that has worked for me in the past:
>
> ObjCmd.Execute RecordsAffected
>
> Note the absent values for parameters and option.
>
> It seems to me that when I make the original call, it accepts
> the null as my new parameter list, doing who knows what to my existing
> parameters.
>
> So how does Delphi call an object that has optional parameters
> without passing data?
>
> I would think that this had been covered years ago, but I
> failed in my search for knowledge.
>
> Rich
>

• Previous message: treok: "Re: SQL ORDER BY as parameter"
• In reply to: Rich: "Using parameters with the low level ADO API, trying to avoid the memory leaks."
• Next in thread: Rich S.: "Re: Using parameters with the low level ADO API, trying to avoid the memory leaks."
• Reply: Rich S.: "Re: Using parameters with the low level ADO API, trying to avoid the memory leaks."
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