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JDBC Statement

Jakob Jenkov
Last update: 2019-02-27

The Java JDBC Statement, java.sql.Statement, interface is used to execute SQL statements against a relational database. You obtain a JDBC Statement from a JDBC Connection. Once you have a Java Statement instance you can execute either a database query or an database update with it. This Java JDBC Statement tutorial will explain how you use a Statement to execute queries, updates, and how to properly close the Statement instance when you are done with it.

Create Statement

In order to use a Java JDBC Statement you first need to create a Statement. Here is an example of creating a Java Statement instance:

Statement statement = connection.createStatement();

The connection instance is a Java JDBC Connection instance.

Executing a Query via a Statement

Once you have created a Java Statement object, you can execute a query against the database. You do so by calling its executeQuery() method, passing an SQL statement as parameter. The Statement executeQuery() method returns a Java JDBC ResultSet which can be used to navigate the response of the query. Here is an example of calling the Java JDBC Statement executeQuery() and navigating the returned ResultSet:

String sql = "select * from people";

ResultSet result = statement.executeQuery(sql);

while(result.next()) {

    String name = result.getString("name");
    long   age  = result.getLong  ("age");

}

Remember that the ResultSet needs to be closed when you are done with it.

Execute an Update via a Statement

You can also execute an update of the database via a Java JDBC Statement instance. For instance, you could execute an SQL insert, update or delete via a Statement instance. Here is an example of executing a database update via a Java JDBC Statement instance:

Statement statement = connection.createStatement();

String    sql       = "update people set name='John' where id=123";

int rowsAffected    = statement.executeUpdate(sql);

The rowsAffected returned by the statement.executeUpdate(sql) call, tells how many records in the database were affected by the SQL statement.

Closing a Statement

Once you are finished with a Statement instance you need to close it. You close a Statement instance by calling its close() method. Here is an example of closing a Java JDBC Statement instance:

statement.close();

Closing a Statement Using Java Try With Resources

In order to close a Statement correctly after use, you can open it inside a Java Try With Resources block. Here is an example of closing a Java JDBC Statement instance using the try-with-resources construct:

try(Statement statement = connection.createStatement()) {
    //use the statement in here.
} catch(SQLException e) {

}

Once the try block exits, the Statement will be closed automatically.

Statement vs. PreparedStatement

The Java JDBC API has an interface similar to the Statement called PreparedStatement . The PreparedStatement can have parameters inserted into the SQL statement, so the PreparedStatement can be reused again and again with different parameter values. You cannot do that with a Statement. A Statement requires a finished SQL statement as parameter.

Jakob Jenkov




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