String sql = "insert into article values (null, 0, ?, ?, ?, now(), 0)";
 PreparedStatement pstmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
 Statement stmt = conn.createStatement();
 
 pstmt.setInt(1, -1);
 pstmt.setString(2, title);
 pstmt.setString(3, cont);
 pstmt.executeUpdate();
 
 ResultSet rsKey = pstmt.getGeneratedKeys();
 rsKey.next();
 int key = rsKey.getInt(1);
 rsKey.close();
 stmt.executeUpdate("update article set rootid = " + key + " where id = " + key);

抛出的异常为：java.sql.SQLException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'id = 11' at line 1

用的是MySQL数据库，数据库中的表是这样建立的：

create table article (
id int primary key auto_increment,
pid int,
rootid int,
title varchar(255),
cont text,
pdate datetime,
isleaf int
);