MySQL Connector/J 5.1 Developer Guide
Statement
objects allow you to execute
basic SQL queries and retrieve the results through the
ResultSet
class, which is described later.
To create a Statement
instance, you call
the createStatement()
method on the
Connection
object you have retrieved using
one of the DriverManager.getConnection()
or
DataSource.getConnection()
methods described
earlier.
Once you have a Statement
instance, you
can execute a SELECT
query by
calling the executeQuery(String)
method
with the SQL you want to use.
To update data in the database, use the
executeUpdate(String SQL)
method. This
method returns the number of rows matched by the update
statement, not the number of rows that were modified.
If you do not know ahead of time whether the SQL statement will
be a SELECT
or an
UPDATE
/INSERT
,
then you can use the execute(String SQL)
method. This method will return true if the SQL query was a
SELECT
, or false if it was an
UPDATE
,
INSERT
, or
DELETE
statement. If the
statement was a SELECT
query, you
can retrieve the results by calling the
getResultSet()
method. If the statement was
an UPDATE
,
INSERT
, or
DELETE
statement, you can
retrieve the affected rows count by calling
getUpdateCount()
on the
Statement
instance.
Example 6.2 Connector/J: Using java.sql.Statement to execute a
SELECT
query
import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; import java.sql.ResultSet; // assume that conn is an already created JDBC connection (see previous examples) Statement stmt = null; ResultSet rs = null; try { stmt = conn.createStatement(); rs = stmt.executeQuery("SELECT foo FROM bar"); // or alternatively, if you don't know ahead of time that // the query will be a SELECT... if (stmt.execute("SELECT foo FROM bar")) { rs = stmt.getResultSet(); } // Now do something with the ResultSet .... } catch (SQLException ex){ // handle any errors System.out.println("SQLException: " + ex.getMessage()); System.out.println("SQLState: " + ex.getSQLState()); System.out.println("VendorError: " + ex.getErrorCode()); } finally { // it is a good idea to release // resources in a finally{} block // in reverse-order of their creation // if they are no-longer needed if (rs != null) { try { rs.close(); } catch (SQLException sqlEx) { } // ignore rs = null; } if (stmt != null) { try { stmt.close(); } catch (SQLException sqlEx) { } // ignore stmt = null; } }