尝试创建准备好的语句来更新 MySQL 时出错

问题描述

我是 Java 新手，正在尝试习惯语法并将数据推送到 MysqL 表。我遇到了这个问题，无法弄清楚我做错了什么。执行我的更新命令时出现以下错误。

java.sql.sqlSyntaxErrorException: 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 ''occupation' = 'cat' WHERE first_name = 'kevin' AND last_name = 'hudgens'' at line 1
        at com.MysqL.cj.jdbc.exceptions.sqlError.createsqlException(sqlError.java:120)
        at com.MysqL.cj.jdbc.exceptions.sqlExceptionsMapping.translateException(sqlExceptionsMapping.java:122)
        at com.MysqL.cj.jdbc.ClientPreparedStatement.executeInternal(ClientPreparedStatement.java:953)
        at com.MysqL.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1092)
        at com.MysqL.cj.jdbc.ClientPreparedStatement.executeUpdateInternal(ClientPreparedStatement.java:1040)
        at com.MysqL.cj.jdbc.ClientPreparedStatement.executeLargeUpdate(ClientPreparedStatement.java:1347)
        at com.MysqL.cj.jdbc.ClientPreparedStatement.executeUpdate(ClientPreparedStatement.java:1025)
        at Driver.updateContact(Driver.java:172)
        at Main.main(Main.java:119)

主文件

System.out.println("Please enter the first name of the contact you want to update.");
                                first_name = input.nextLine();
                                System.out.println("Please enter the last name of the contact you want to update.");
                                last_name = input.nextLine();

                                System.out.println("Are you sure you want to update " + first_name + " " + last_name
                                                + "'s information. YES or NO");

                                String verifyUpdate = input.nextLine();
                                // lower for comparison
                                // verifyUpdate = verifyUpdate.toLowerCase();

                                if (verifyUpdate.equals("YES")) {
                                        break;
                                } else if (verifyUpdate.equals("NO")) {
                                        System.out.println(
                                                        "Please enter the correct first and last name of the contact you would like to update");
                                } else {
                                        System.out.println("You didnt enter the correct answer. YES or NO");
                                }
                        }
                        // inform user what they can update
                        System.out.println("What would you like to update? Options are:"
                                        + "\nFirsT NAME \n LAST NAME \n PHONE NUMBER \n EMAIL \n OCCUPATION");

                        // Collect the choices
                        String updateColumnChoice = input.nextLine();
                        System.out.println("What would you like to update it to? ");
                        String updatedValue = input.nextLine();

                        driver.updateContact(first_name,last_name,updateColumnChoice,updatedValue);

这是准备好的语句

public static void updateContact(String first_name,String last_name,String updatedColumn,String toBeUpdatedValue) {
    try {
        // Get connection to database
        Connection myConn = DriverManager.getConnection(info);

        // Create sql command for deleting
        String query = "UPDATE contacts SET ? = '?' WHERE first_name = '?' AND last_name = '?' ";

        PreparedStatement preparedStmt = myConn.prepareStatement(query);
        preparedStmt.setString(1,updatedColumn);
        preparedStmt.setString(2,toBeUpdatedValue);
        preparedStmt.setString(3,first_name);
        preparedStmt.setString(4,last_name);

        // push prepared statement to the database
        preparedStmt.executeUpdate();

        // close the connection to the database
        myConn.close();
    } catch (Exception exc) {
        exc.printstacktrace();
    }
}

对此的任何帮助将不胜感激。以及对我的代码的任何普遍批评。

解决方法

据我所知，您只能将 PreparedStatement 的参数用于值，不能用于元数据。如果您需要 updatedColumn 是动态的，您可以这样做：

String query = "UPDATE contacts SET " + updatedColumn + " = '?' WHERE first_name = '?' AND last_name = '?' ";

请注意，您必须确保 updatedColumn 被正确引用/转义，特别是如果它来自用户数据（即 SQL 注入攻击）。