(初学者)eclipse编写java 对数据库的操作问题，不知道问题出在哪里，无法入库

Question

代码如下：
QueryRunner queryRunner = new QueryRunner();

    String sql = "delete from customers where id = ?";

    Connection connection = null;
    try {

        connection = JDBCTools.getConnection();
        System.out.println(connection);
        System.out.println(queryRunner);

        int i = queryRunner.update(connection, sql,1);
        if(i > 0){
            System.out.println("成功");
        }else {
            System.out.println("失败");
        }
    } catch (Exception e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }finally {
        JDBCTools.releaseDB(null, null, connection);
    }

Answer 1

sql语句和所用的方法都是不对的，好好看看