“参数索引超出范围（3 > 参数数量，即 2）。” 更新表时

Question

我正在为大学做的期末项目需要帮助，我正在做一个图书馆类系统。我是 mySQL 的新手。我在代码上遇到问题，“参数索引超出范围（3 > 参数数量，即 2）”。PreparedStatement book_edit = book_db.prepareStatement("update books set ?='?' where id=?");            book_edit.setString(1, column); //where column is to set the column of the table            book_edit.setString(2, input); //where input is what you want to change            book_edit.setInt(3, book_id); //the primary key in my database            int i = book_edit.executeUpdate();            if (i != 0) {                System.out.println("UPDATED!!");            }            else {                System.out.println("Failed to Add Data!");            }

Answer 1

列名不能是 的变量PreparedStatement。它必须是 SQL 的一部分String：

PreparedStatement book_edit = book_db.prepareStatement("update books set " + column + "= ? where id = ?");

book_edit.setString(1, input); //where input is what you want to change

book_edit.setInt(2, book_id); //the primary key in my database