How big is an nvarchar(max) as far as ADO is concerned? - delphi

Question

i am trying to use a parameterized query against ADO:
INSERT INTO Foo (Name, Value) VALUES(#name, #value)
In SQL Server the Name column is a varchar type. The Value column is an nvarchar(max).
What size do i pass when creating a parameter when i don't know, or want to specify, the size?
procedure SaveTheThing(Connection: TADOConnection);
var
sql: WideString;
cmd: _Command;
begin
sql := 'INSERT INTO Foo (Name, Value) VALUES(#name, #value)';
cmd := CoCommand.Create;
cmd.Set_ActiveConnection(Connection.ConnectionObject);
cmd.Set_CommandType(adCmdText);
cmd.Set_CommandText(sql);
//and now add the parameters
cmd.Parameters.Append(
cmd.CreateParameter('#name', adVarChar, adParamInput, -1, filename)
);
cmd.Parameters.Append(
cmd.CreateParameter('#value', adVarWChar, adParamInput, -1, GetXmlToWideString)
);
cmd.Execute({out}recordsAffected, EmptyParam, adCmdSomeThatDoesntCauseAnExcetpion or adExecuteNoRecords);
end;
The simple alternative was going to be:
sql := 'INSERT INTO Foo (Name, Value)'#13#10+
'VALUES (+QuotedStr(filename)+', '+QuotedStrW(GetXmlToWideString)+')';
and be done already. But i thought i'd burn a few days trying to make parameterized queries a viable solution, and avoid having to write a QuotedStrW.

Answer 1

You can use the -1 value in the size of a ADO parameter without problems.
Try this sample code , which insert a 2MB string in the Value column
var
sql: WideString;
cmd: _Command;
recordsAffected : OleVariant;
begin
sql := 'INSERT INTO Foo (Name, Value) VALUES(?, ?)';
cmd := CoCommand.Create;
cmd.Set_ActiveConnection(Connection.ConnectionObject);
cmd.Set_CommandType(adCmdText);
cmd.Set_CommandText(sql);
//and now add the parameters
cmd.Parameters.Append(cmd.CreateParameter('#name', adVarChar, adParamInput, -1, 'AfileName'));
cmd.Parameters.Append(cmd.CreateParameter('#value', adVarWChar, adParamInput, -1, StringOfChar('#', 2*1024*1024)));
cmd.Execute({out}recordsAffected, EmptyParam, adExecuteNoRecords);
end;

Answer 2

You can use my answer on your other post:
"Must declare the variable #myvariable" error with ADO parameterized query
to use parameters and parameter by name. Try to avoid using _Command, but use TADOCommand because it is more friendly (and simpler to code too). You can assign parameter to a value by using:
Parameters.ParamByName('xxxx').value := someValue.
Of course someValue data type must correspond to your SQL server column data type definition.