Connection to MySQL Database from Delphi, C++Builder, and Lazarus

1. Find the TMyConnection component in the MyDAC category on the Tool Palette.
2. Double-click the component. A new object will appear on the form. If this is the first time that you create a TMyConnection object in this project, the object will be named MyConnection1. Using TMyConnection Editor.

Using TMyConnection Editor

1. Double-click the MyConnection1 object.
2. Specify the DNS name or IP address of the MySQL server in the Server edit box.
3. If you use a port other than the default port 3306, specify it in the Port edit box.
4. Specify the database name in the Database edit box.
5. Specify the username (root by default) in the Username edit box.
6. Specify the password (empty value by default) in the Password edit box.

Using Object Inspector

1. Select the MyConnection1 object on the form.
2. Set the Database property to the database name.
3. Set the Password property to the password (root by default).
4. If you use a port other than the default port 3306, set the Port property to your port.
5. Set the Server property to the DNS name or IP address of the MySQL server.
6. Set the Username property to the username (empty value by default).

1. Run RAD Studio and select File -> New – > VCL Forms Application – Delphi.
2. Place the TCRSSLIOHandler component into the form to connect MyDAC to the MySQL server through SSL. Also add the TMyConnection, TMyQuery, TDataSource, TDBGrid, and TButton components to the form.
3. Select the TMyConnection component and asign the TCRSSLIOHandler object to the IOHandler property in the Object Inspector.
4. Expand Options and set the Protocol property to mpSSL.
5. Expand SSLOptions in the Object Inspector and specify the server certificate in the CACert property, the client certificate in the Cert property, and the private client key in the Key property.
Double-click TMyConnection and specify the server address, port, username, password, and, optionally, database name. Click Connect to test connection to the MySQL server.
6. Select the TDataSource component and assign the MyQuery1 object to the DataSet property.
7. Assign the DataSource1 object to the DataSource property in the TDBGrid component.
8. Double-click the TMyQuery component and add a SQL query that will be run against the MySQL database.
9. Select the TButton component and create the OnClick event. Add the code that will call the Open method in the TMyQuery component when you click the button.
10. Press F9 to compile and run the application. Click the button on the form to execute the query and display data in the grid.

First of all, you should find out what causes the problem. The list of most frequent reasons for this error to occur is below.

• • Client side: The value of TMyConnection.ConnectionTimeout or TCustomMyDataSet.CommandTimeout is too small. To check this hypothesis, try setting TCustomMyDataSet.CommandTimeout to 0 (infinitive) and TMyConnection.ConnectionTimeout to 300.
• • Server side: MySQL server has closed the connection. You can read a detailed description of all possible reasons for this to happen in the MySQL Reference Manual. Almost always it is because the value of wait_timeout variable is too small. Try increasing it. If this solution is not possible (for example, because you don't have enough rights), you should invoke MyConnection.Ping with an interval less than wait_timeout. Use TTimer in TMyConnection thread to accomplish this task.
• • Unstable connection (GPRS etc). In case of unstable connection you can adapt MyDAC to work in such conditions by changing some of its settings. For more information please see the "Working in Unstable Networks" article in the MyDAC help documentation.

If the connection is lost, MyDAC tries to reconnect to server. However, your last command will probably not be executed, and you should repeat it again. MyDAC does not try to reconnect if a transaction has started or if at least one of statements is prepared.