Jaybird 2.1 JDBC driver Java Programmer's Manual - Firebird

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Statement stmt = connection.createStatement();
try {
ResultSet rs = stmt.executeQuery(
"SELECT firstName, lastName FROM users" +
" WHERE userId = 5");
rs.next();
String firstName = rs.getString(1);
String lastName = rs.getString(2);
} finally {
stmt.close();
}
Illustration 4.1: Typical way to execute query to get information about the user.
1. Create a Statement object by calling the createStatement() method of the
Connection object.
2. Use the Statement object by calling its methods, in our case we execute simple
query SELECT firstName, lastName FROM users WHERE userId = 5.
Processing of the query result will be discussed in details in the next chapter.
3. Close the statement to release all allocated resources. In our example this is
done in the finally section of the try/finally block.
The fact that connection object is a factory for the statement objects puts a
constraint on the object lifetime – statements are bound to the connection; when
the connection is closed, all statements that were created by that connection
become invalid and the resources allocated by them are released. However,
despite that fact that the resources are finally released, it is strongly recommended
to use the try/finally block, to guarantee that resources are released as soon as
possible because of the reasons that will be discussed later.
Statement can be executed using the following methods:
• Statement.executeQuery(String) – executes a SELECT statement and
returns a result set. If the specified statement is not a SELECT statement, an
SQLException is thrown after the statement execution.
• Statement.executeUpdate(String) – executes INSERT, UPDATE,
DELETE or DDL 1 statements and returns the number of updated rows. If the
specified statement is a query, an SQLException is thrown.
• Statement.execute(String) – executes a statement and returns true when
the statement returned a result set, otherwise an update was executed and false
is returned. You can use Statement.getResultSet() method to get the result
of the executed query or you can use Statement.getUpdateCount() when you
have executed update statement.
Statement is closed by calling the Statement.close() method. After this the
statement object is invalid and cannot be used anymore.
1 DDL – Data Definition Language. This term is used to group all statements that are used to
manipulate database schema, i.e. creation of tables, indices, views, etc.
Chapter 4. Executing statements 34