The JDBC Test controller is a generative controller whose function is to create a single test case for FTP applications. The JDBC Test allows you to configure an FTP sample:

• Username: Username to use to connect to server
• Password: Password to user to connect to server
• Database URL: This includes the host name plus database name. It should be in the correct format for the database being tested (usually hostname/database name)
• Sub Protocol: The sub-protocol to use with your specific database (ie "mysql" for MySQL)
• Driver Class: The full class name of your driver (ie org.gjt.mm.mysql.Driver)
• Number of Connections in Pool: JMeter will use a pool of connections that you can configure. Set here how many connections you would like the pool to maintain
• Max usage for each connection: JMeter will automatically re-initialize SQL connections that have been used a certain number of times. You can change the max usage for each connection here.
• SQL Query String: Finally, the actual SQL query you want to test.

Note: If you were going to test multiple SQL queries, you would probably want to add a "Database Login" config element to the top of your test tree, and configure the username, password, database URL, sub-protocol, and Driver class in just the one place. You can similarly add a "Database Connection Pool" config element.