Using the Statement or PreparedStatement Interface

The following must be considered when using the Statement or PreparedStatement interface:

  • You can use a single Statement instance as many times as you want. You could create one as soon as you open the connection and use it for the connection's lifetime. But you have to remember that only one ResultSet can exist per Statement or PreparedStatement at a given time.
  • If you need to perform a query while processing a ResultSet, you can simply create and use another Statement.
  • If you are using threads, and several are using the database, you must use a separate Statement for each thread. Refer to Chapter 10, Using the Driver in a Multithreaded or a Servlet Environment if you are thinking of using threads, as it covers some important points.
  • When you are done using the Statement or PreparedStatement you should close it.
  • In JDBC, the question mark (?) is the placeholder for the positional parameters of a PreparedStatement. There are, however, a number of PostgreSQL operators that contain a question mark. To keep such question marks in a SQL statement from being interpreted as positional parameters, use two question marks (??) as escape sequence. You can also use this escape sequence in a Statement, but that is not required. Specifically only in a Statement a single (?) can be used as an operator.
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