How to update a DateTime on SQL Server preserving milliseconds using Delphi 7 ADOQuery.ExecSQL?

Question

How do you update a DateTime on SQL Server 2012 preserving milliseconds using Delphi 7 ADOQuery.ExecSQL?

SQL server seems to drop the seconds precision so I do not have milliseconds or microseconds on a SQL Server 2012 DateTime2[7] field. MS Access does not drop the milliseconds with this ADO Query. The following ADOQuery code seems to work with all DataTypes that I care about except SQL Server DateTime.

The connection string I am using is: Provider=SQLNCLI11.1;Integrated Security=SSPI;User ID="";Initial File Name="";Server SPN="";Data Source=myPC\SQLSERVER2012EXP;Initial Catalog=MyDatabase

Here is my code:

function ExecuteNonQry(Conn:TADOConnection;Sql:string;Params:Variant): Integer;
{ Execute a query that does not return a recordset.  Returns number of rows 
  affected. Params can be any unique name, they are all dealt with in order
  of appearance in the parameter array and in the sql string.
  E.g. SQL 
    'INSERT INTO customers (id,name,country) VALUES (:id,:name,:country)';
  E.g. calling code:
    sql := 
     'INSERT INTO Sessions (SessionType_cod , HasErrors, Start_Timestamp) ' + 
     ' VALUES (:1, :2, :3)';
    params := VarArrayOf([ 1, true, Now ]);
    ExecuteNonQry( GvConnection1, sql, params );

    Note: Do not use ADO with Paradox - will be slow and possibly error prone.

    Tested the following DataTypes with "Insert Into" and "Update" queries
    **********************************************************************
    Delphi          MS Access    SQL Server      Paradox
    -----------------------------------------------------
    ftInteger       Long         int
    ftString        Text(255)    nvarchar(255)
    ftString        Memo         nvarchar(max)
    ftBoolean       Boolean      bit
    ftDateTime      Date         datetime2(7)
    ftDouble        Double       float
}
var
  qry : TADOQuery;
begin
  assert( Conn <> nil);
  assert( Sql <> '');
  qry := TADOQuery.Create(nil);
  qry.DisableControls;
  qry.SQL.Text := Sql;
  AddParametersToQuery(qry, Params);
  qry.Connection := Conn;
  result := qry.ExecSQL;
end;

procedure AddParametersToQuery(var Qry: TADOQuery; Params: Variant);
{ Version 1b.  (Uses Delphi function to replace "DIRegEx" dependencies)
  Add parameters (type and value) to ADO query. ADOQuery must have SQL 
  text set and Params is a variant array. 
  Limitations: SQL Server drops DateTime second precision digits for 
  milliseconds or microseconds.
  E.g. Sql: 
    'INSERT INTO Sessions (SessionType_cod , HasErrors, Start_Timestamp) 
     VALUES (:1, :2, :3)';
  or  Sql: 
    'INSERT INTO Sessions (SessionType_cod , HasErrors, Start_Timestamp) 
     VALUES (:mykey, :HasErrors, :myDateTime)';
}
const
  regPattern = ':';
var
  str: String;
  val: Variant;
  i: Integer;
  sl: TStrings;
begin
  assert( Qry.SQL.Text <> '');

  // in some cases this is necessary.
  Qry.Parameters.ParseSQL(Qry.SQL.Text, true);        

  sl := TStringList.Create;
  try
    // find all param wordssql text such as '1, 2, 3'
    sl := ExtractWordsToStrings(':', Qry.SQL.Text);   

    // loop through any matches found
    for i := 0 to sl.Count -1 do            
    begin
      str := sl[i];
      val := GetVarParam(i, Params);
      // in some cases this is necessary.
      Qry.Parameters.ParamByName(str).DataType := 
          VarTypeToDataType(Ord(VarType(val)) );
      Qry.Parameters.ParamByName(str).Value := val;
    end;
  finally
    sl.Free;
  end;
end;

UPDATED

Modified code for MS Access and SQL Server:

if (VarType(val) = varDate) And IsSqlServerProvider(Conn.Provider) then begin
  // needed for SQL Server
  Qry.Parameters.ParamByName(str).Value := 
     FormatDateTime('yyyymmdd hh:nn:ss.zzz', val)   
end
else
begin
  // in some cases this is necessary.
  Qry.Parameters.ParamByName(str).DataType := 
     VarTypeToDataType(Ord(VarType(val))); 
  Qry.Parameters.ParamByName(str).Value := val;
end;

Answer 1

DateTime2(7) via Ado is seen as TWideStringField.
Datetime will be seen as TDateTimeField.
Internal conversion if assigning a TDatetime will ignore milliseconds like DateTimeToStr(dt).
You can handle this by using own conversion to WideString.

Function MyDateTimeString(d:TDateTime):String;
begin
  Result := FormatDateTime('yyyymmdd hh:nn:ss.zzz',d);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
dt:TdateTime;
begin
  dt := now;
  Caption := FormatDateTime('dd.mm.yyyy hh:nn:ss.zzz',dt);
  Adoquery1.Paramcheck := true;
  Adoquery1.SQL.Text := 'Insert into Tab (a,b,DT) Values (:a,:b,:DT)';
  Adoquery1.Parameters.ParseSQL(Adoquery1.SQL.Text,true);
  Adoquery1.Parameters.ParamByName('a').Value := 1;
  Adoquery1.Parameters.ParamByName('b').Value := 2;
  Adoquery1.Parameters.ParamByName('DT').Value := MyDateTimeString(dt);
  Adoquery1.ExecSQL;
end;

using then following will lead to rounding:

  Adoquery1.Parameters.ParamByName('DT').DataType := ftDateTime;
  Adoquery1.Parameters.ParamByName('DT').Value := dt;