Java Enterprise in a Nutshell, Second Edition

Statements

Once you have created a Connection, you can begin using it to execute SQL statements. This is usually done via Statement objects. There are actually three kinds of statements in JDBC:

Statement

Represents a basic SQL statement

PreparedStatement

Represents a precompiled SQL statement, which can offer improved performance

CallableStatement

Allows JDBC programs complete access to stored procedures within the database itself

We’re just going to discuss the Statement object for now; PreparedStatement and CallableStatement are covered in detail later in this chapter.

To get a Statement object, call the createStatement( ) method of a Connection:

Statement stmt = con.createStatement(  );

Once you have created a Statement, use it to execute SQL statements. A statement can either be a query that returns results or an operation that manipulates the database in some way. If you are performing a query, use the executeQuery( ) method of the Statement object:

ResultSet rs = stmt.executeQuery("SELECT * FROM CUSTOMERS");

Here we’ve used executeQuery( ) to run a SELECT statement. This call returns a ResultSet object that contains the results of the query (we’ll take a closer look at ResultSet in the next section).

Statement also provides an executeUpdate( ) method, for running SQL statements that don’t return results, such as the UPDATE and DELETE statements. executeUpdate( ) returns an integer that indicates the number of rows in the database that were altered.

If you don’t know whether ...