Java Programming with Oracle JDBC

The executeQuery( ) Method

Now that you’ve learned how to insert, update, and delete data in a table, it’s time to learn how to use a SELECT statement to retrieve data. Whereas the execute( ) and executeUpdate( ) methods discussed in previous sections return primitive data types -- a boolean and int, respectively -- the method normally used with a SELECT statement, executeQuery( ), returns a ResultSet object. The executeQuery( ) method effectively combines the execute( ) and getResultSet( ) methods into one call:

ResultSet rset = null;
Statement stmt = null;
try {
  stmt = conn.createStatement(  );
  rset = stmt.executeQuery("select last_name, first_name from person"); 
  . . . 
}

In this example, we once again assume that a Connection object, conn, already exists. The example starts out by declaring a ResultSet variable, rset, to hold the reference to the ResultSet object generated by the SQL statement. Next, it declares a Statement variable, stmt, to hold the reference to a Statement object. In the try block, the Statement object is created and stored in stmt using the Connection object’s createdStatement( ) method. Then, the Statement object’s executeQuery( ) method is called to execute the SQL SELECT statement, returning a ResultSet into rset.

A ResultSet (which we will cover in great detail in Chapter 10) is an object that has a set of accessor methods that allow you to get to the data returned from the database. These include methods for positioning the cursor, doing in-place updates, ...