5.4 Preparing Statements in Connector/NET

Prepared statements can provide significant performance improvements on queries that are executed more than one time. Prepared execution is faster than direct execution for statements executed more than once, primarily because the query is parsed only one time. In the case of direct execution, the query is parsed every time it is executed. In addition, prepared execution can provide a reduction of network traffic because for each execution of the prepared statement, it is necessary only to send the data for the parameters.

Another advantage of prepared statements is that, with server-side prepared statements enabled, it uses a binary protocol that makes data transfer between client and server more efficient.

To prepare a statement, use the following sequence of steps:

1. Create a MySqlCommand object and set the CommandText property to your query.

2. After entering your statement, call the Prepare method of the command object. When the statement is prepared, add parameters for each of the dynamic elements in the query.

3. Execute the statement using the ExecuteNonQuery(), ExecuteScalar(), or ExecuteReader methods.

For subsequent executions, you need only modify the values of the parameters and call the execute method again, there is no need to set the CommandText property or redefine the parameters.

C# Code Example

MySql.Data.MySqlClient.MySqlConnection conn;
MySql.Data.MySqlClient.MySqlCommand cmd;

conn = new MySql.Data.MySqlClient.MySqlConnection();
cmd = new MySql.Data.MySqlClient.MySqlCommand();

conn.ConnectionString = strConnection;

try
{
    conn.Open();
    cmd.Connection = conn;

    cmd.CommandText = "INSERT INTO myTable VALUES(NULL, @number, @text)";
    cmd.Prepare();

    cmd.Parameters.AddWithValue("@number", 1);
    cmd.Parameters.AddWithValue("@text", "One");

    for (int i=1; i <= 1000; i++)
    {
        cmd.Parameters["@number"].Value = i;
        cmd.Parameters["@text"].Value = "A string value";

        cmd.ExecuteNonQuery();
    }
}
catch (MySql.Data.MySqlClient.MySqlException ex)
{
    MessageBox.Show("Error " + ex.Number + " has occurred: " + ex.Message,
        "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}

Visual Basic Code Example

Dim conn As New MySqlConnection
Dim cmd As New MySqlCommand

conn.ConnectionString = strConnection

Try
   conn.Open()
   cmd.Connection = conn

   cmd.CommandText = "INSERT INTO myTable VALUES(NULL, @number, @text)"
   cmd.Prepare()

   cmd.Parameters.AddWithValue("@number", 1)
   cmd.Parameters.AddWithValue("@text", "One")

   For i = 1 To 1000
       cmd.Parameters("@number").Value = i
       cmd.Parameters("@text").Value = "A string value"

       cmd.ExecuteNonQuery()
     Next
Catch ex As MySqlException
    MessageBox.Show("Error " & ex.Number & " has occurred: " & 
    ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error)
End Try