第1行的SQL语法错误

debugcn 发表于 Dev

青色

我正在尝试使用Java中的MySQL创建考试，不允许重复编号。

我很难找到我的错误。我已经调试了几个小时的代码。

错误：您的SQL语法有错误。检查与您的MySQL服务器版本相对应的手册，以在第1行的'null WHERE number = 1'附近使用正确的语法

下面是我的代码

    String examNames = examName.getName();
    String searchNumber = "SELECT * FROM " + examNames + " WHERE number = ?";
    PreparedStatement preparedNumber = connect.prepareStatement(searchNumber);
    int examNumbers = Integer.parseInt(textNumber.getText());
    preparedNumber.setInt(1, examNumbers);
    ResultSet results = preparedNumber.executeQuery();
    if (results.next()) {
        JOptionPane.showMessageDialog(null, "Exam number was already added");
    }

    else {
        String examLabel = examName.getText();
        String insertContent = " Insert INTO " + examLabel
                + "(number, content, choiceA, choiceB, choiceC, choiceD, correctans) values(?,?,?,?,?,?,'"
                + correctAns + "')";
        PreparedStatement preparedStatement = connect.prepareStatement(insertContent);
        int examNumber = Integer.parseInt(textNumber.getText());
        String content = textAreaQuestion.getText();
        String choiceA = textAreaA.getText();
        String choiceB = textAreaB.getText();
        String choiceC = textAreaC.getText();
        String choiceD = textAreaD.getText();
        String correct = correctAns;
        preparedStatement.setInt(1, examNumber);
        preparedStatement.setString(2, content);
        preparedStatement.setString(3, choiceA);
        preparedStatement.setString(4, choiceB);
        preparedStatement.setString(5, choiceC);
        preparedStatement.setString(6, choiceD);
        preparedStatement.executeUpdate();
        JOptionPane.showMessageDialog(null, "Added");
    }

可怕的袋熊

如果说

'null WHERE number = 1'

那就意味着

String examNames= examName.getName();

返回null

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