TADOQuery Class

TADOQuery provides the means for issuing SQL against an ADO data store.

Pascal

TADOQuery = class(TCustomADODataSet);

C++

class TADOQuery : public TCustomADODataSet;

File

ADODB

Description

Use TADOQuery to access one or more tables in a data store using SQL statements.

Retrieve data from tables in an ADO data store using SELECT statements. Perform actions on tables and other metadata objects in an ADO data store with statements like INSERT, DELETE, UPDATE, ALTER TABLE, and CREATE TABLE. Execute stored procedures.

C++ Examples:

Copy Code

//
//This example demostrates the use of ADO for database conectivity.
//Example assumes that a TDBGrid is placed on the form.
//
void __fastcall TForm2::FormCreate(TObject *Sender)
{
    /* Login details */
    String UserName = "db_user_name";
    String PassWord = "db_pass_word";
    String Server = "my.db.server";

    /* Connection String */
    String ConnString =
        "Provider=SQLOLEDB.1;Persist Security Info=False;";
    ConnString +=
        "User ID=%s;Password=%s;Data Source=%s;Use Procedure for Prepare=1;";
    ConnString +=
        "Auto Translate=True;Packet Size=4096;Use Encryption for Data=False;";
    ConnString +=
        "Tag with column collation when possible=False";

    /* SQL Query */
    String SQLStr = "SELECT * FROM customer WHERE customer_id = :AnId;";

    /* All ADO variables */
    TADOConnection* ADOConn;
    TADOQuery* ADOQuery;
    TDataSource* DataSrc;
    TParameter* Param;

    /* Create an ADO connection */
    ADOConn = new TADOConnection(this);

    /* Setup the connection string */
    ADOConn->ConnectionString = Format(ConnString,
        ARRAYOFCONST((UserName, PassWord, Server)));

    /* Disable login prompt */
    ADOConn->LoginPrompt = False;

    try
    {
        ADOConn->Connected = true;
    }
    catch (EADOError *e)
    {
        MessageDlg("Error while connecting", mtError,
                      TMsgDlgButtons() << mbOK, 0);
        return;
    }

    /* Create the query */
    ADOQuery = new TADOQuery(this);
    ADOQuery->Connection = ADOConn;
    ADOQuery->SQL->Add(SQLStr);

    /* Update the parameter that was parsed from the SQL query: AnId */
    Param = ADOQuery->Parameters->ParamByName("AnId");
    Param->DataType = ftInteger;
    Param->Value = 1;

    /* Set the query to Prepared - will improve performance */
    ADOQuery->Prepared = true;

    try
    {
        ADOQuery->Active = true;
    }
    catch (EADOError *e)
    {
        MessageDlg("Error while connecting", mtError,
                      TMsgDlgButtons() << mbOK, 0);
        return;
    }

    /* Create the data source */
    DataSrc = new TDataSource(this);
    DataSrc->DataSet = ADOQuery;
    DataSrc->Enabled = true;

    /* Finally initilalize the grid */
    DBGrid1->DataSource = DataSrc;
}

Delphi Examples:

Copy Code

{
This example demostrates the use of ADO for database conectivity.
Example assumes that a TDBGrid is placed on the form.
}
procedure TForm2.FormCreate(Sender: TObject);
const
  { Connection string }
  ConnString =
  'Provider=SQLOLEDB.1;Persist Security Info=False;' +
  'User ID=%s;Password=%s;Data Source=%s;Use Procedure for Prepare=1;' +
  'Auto Translate=True;Packet Size=4096;Use Encryption for Data=False;'+
  'Tag with column collation when possible=False';

  { SQL Query }
  SQLStr = 'SELECT * FROM customer WHERE customer_id = :AnId;';

  { User access }
  UserName = 'db_user_name';
  PassWord = 'db_pass_word';
  Server = 'my.db.server';

var
  ADOConn  : TADOConnection;
  ADOQuery : TADOQuery;
  DataSrc  : TDataSource;
  Param    : TParameter;

begin
  { Create an ADO connection }
  ADOConn := TADOConnection.Create(Self);
  { Setup the provider engine }

  { Setup the connection string }
  ADOConn.ConnectionString := Format(ConnString,
    [UserName, PassWord, Server]);

  { Disable login prompt }
  ADOConn.LoginPrompt := False;

  try
    ADOConn.Connected := True;
  except
    on e: EADOError do
    begin
      MessageDlg('Error while connecting', mtError,
                  [mbOK], 0);

      Exit;
    end;
  end;

  { Create the query }
  ADOQuery := TADOQuery.Create(Self);
  ADOQuery.Connection := ADOConn;
  ADOQuery.SQL.Add(SQLStr);

  { Update the parameter that was parsed from the SQL query: AnId }
  Param := ADOQuery.Parameters.ParamByName('AnId');
  Param.DataType := ftInteger;
  Param.Value := 1;

  { Set the query to Prepared - will improve performance }
  ADOQuery.Prepared := true;

  try
    ADOQuery.Active := True;
  except
    on e: EADOError do
    begin
      MessageDlg('Error while doing query', mtError,
                  [mbOK], 0);

      Exit;
    end;
  end;

  { Create the data source }
  DataSrc := TDataSource.Create(Self);
  DataSrc.DataSet := ADOQuery;
  DataSrc.Enabled := true;

  { Finally initilalize the grid }
  DBGrid1.DataSource := DataSrc;
end;