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SQL Anywhere 11.0.1 (Français) » SQL Anywhere Server - Programming » SQL Anywhere Data Access APIs » SQL Anywhere .NET Data Provider » Accessing and manipulating data

 

Obtaining primary key values

If the table you are updating has an autoincremented primary key, uses UUIDs, or if the primary key comes from a primary key pool, you can use a stored procedure to obtain values generated by the data source.

When using the SADataAdapter, this technique can be used to fill the columns in the DataSet with the primary key values generated by the data source. If you want to use this technique with the SACommand object, you can either get the key columns from the parameters or reopen the DataReader.

Examples

The following examples use a table called adodotnet_primarykey that contains two columns, ID and Name. The primary key for the table is ID. It is an INTEGER and contains an autoincremented value. The Name column is CHAR(40).

These examples call the following stored procedure to retrieve the autoincremented primary key value from the database.

CREATE PROCEDURE sp_adodotnet_primarykey( out p_id int, in p_name char(40) )
BEGIN
    INSERT INTO adodotnet_primarykey( name ) VALUES(
      p_name );
    SELECT @@IDENTITY INTO p_id;
END
♦  To insert a new row with an autoincremented primary key using the SACommand object
  1. Connect to the database.

    SAConnection   conn = OpenConnection();
  2. Create a new SACommand object to insert new rows into the DataTable. In the following code, the line int id1 = ( int ) parmId.Value; verifies the primary key value of the row.

    SACommand      cmd = conn.CreateCommand();
    cmd.CommandText = "sp_adodotnet_primarykey";
    cmd.CommandType = CommandType.StoredProcedure;
    SAParameter parmId = new SAParameter();
    parmId.SADbType = SADbType.Integer;
    parmId.Direction = ParameterDirection.Output;
    cmd.Parameters.Add( parmId );
    SAParameter parmName = new SAParameter();
    parmName.SADbType = SADbType.Char;
    parmName.Direction = ParameterDirection.Input;
    cmd.Parameters.Add( parmName );
    parmName.Value = "R & D --- Command";
    cmd.ExecuteNonQuery();
    int id1 = ( int ) parmId.Value;
    parmName.Value = "Marketing --- Command";
    cmd.ExecuteNonQuery();
    int id2 = ( int ) parmId.Value;
    parmName.Value = "Sales --- Command";
    cmd.ExecuteNonQuery();
    int id3 = ( int ) parmId.Value;
    parmName.Value = "Shipping --- Command";
    cmd.ExecuteNonQuery();
    int id4 = ( int ) parmId.Value;
  3. Bind the results to the grid on the screen and apply the changes to the database.

    cmd.CommandText = "SELECT * FROM " +
        adodotnet_primarykey";
    cmd.CommandType = CommandType.Text;
    SADataReader dr = cmd.ExecuteReader();
    dataGrid.DataSource = dr;
  4. Close the connection.

    conn.Close();
♦  To insert a new row with an autoincremented primary key using the SADataAdapter object
  1. Create a new SADataAdapter.

    DataSet         dataSet = new DataSet();
    SAConnection   conn = OpenConnection();
    SADataAdapter  adapter = new SADataAdapter();
    adapter.MissingMappingAction =
        MissingMappingAction.Passthrough;
    adapter.MissingSchemaAction =
        MissingSchemaAction.AddWithKey;
  2. Fill the data and schema of the DataSet. The SelectCommand is called by the SADataAdapter.Fill method to do this. You can also create the DataSet manually without using the Fill method and SelectCommand if you do not need the existing records.

    adapter.SelectCommand = new SACommand( "select * from  + adodotnet_primarykey", conn );
  3. Create a new SACommand to obtain the primary key values from the database.

    adapter.InsertCommand = new SACommand(
        "sp_adodotnet_primarykey", conn );
    adapter.InsertCommand.CommandType =
        CommandType.StoredProcedure;
    adapter.InsertCommand.UpdatedRowSource =
        UpdateRowSource.OutputParameters;
    SAParameter parmId = new SAParameter();
    parmId.SADbType = SADbType.Integer;
    parmId.Direction = ParameterDirection.Output;
    parmId.SourceColumn = "ID";
    parmId.SourceVersion = DataRowVersion.Current;
    adapter.InsertCommand.Parameters.Add( parmId );
    SAParameter parmName = new SAParameter();
    parmName.SADbType = SADbType.Char;
    parmName.Direction = ParameterDirection.Input;
    parmName.SourceColumn = "name";
    parmName.SourceVersion = DataRowVersion.Current;
    adapter.InsertCommand.Parameters.Add( parmName );
  4. Fill the DataSet.

    adapter.Fill( dataSet );
  5. Insert the new rows into the DataSet.

    DataRow row = dataSet.Tables[0].NewRow();
    row[0] = -1;
    row[1] = "R & D --- Adapter";
    dataSet.Tables[0].Rows.Add( row );
    row = dataSet.Tables[0].NewRow();
    row[0] = -2;
    row[1] = "Marketing --- Adapter";
    dataSet.Tables[0].Rows.Add( row );
    row = dataSet.Tables[0].NewRow();
    row[0] = -3;
    row[1] = "Sales --- Adapter";
    dataSet.Tables[0].Rows.Add( row );
    row = dataSet.Tables[0].NewRow();
    row[0] = -4;
    row[1] = "Shipping --- Adapter";
    dataSet.Tables[0].Rows.Add( row );
  6. Apply the changes in the DataSet to the database. When the Update method is called, the primary key values are changed to the values obtained from the database.

    adapter.Update( dataSet );
    dataGrid.DataSource = dataSet.Tables[0];

    When you add new rows to the DataTable and call the Update method, the SADataAdapter calls the InsertCommand and maps the output parameters to the key columns for each new row. The Update method is called only once, but the InsertCommand is called by the Update method as many times as necessary for each new row being added.

  7. Close the connection to the database.

    conn.Close();