JDBC连接性CODE错误

Question

我有一个需要Java-Mysql连接的项目。 我一直在尝试通过一个按钮连接两个表，以便在四个JLabel和一个JTextArea中提供输出。

它表明我的SQL语法有错误。

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
  try {
    Class.forName("java.sql.Driver");
    Connection con = DriverManager.getConnection("jdbc:Mysql://localhost/nami", "root", "123456");
    Statement st = con.createStatement();

    String S =
        "Select mobile,state,mobile,email,job from signup where email = " + "mil@gmail.com" + ";";

    String P = "Select INFORMATION FROM pinfo where email = " + "mil@gmail.com" + ";";

    ResultSet rs = st.executeQuery(S);
    ResultSet rs2 = st.executeQuery(P);
    while (rs.next()) {
      String JOB = rs.getString("JOB");
      String state = rs.getString("state");
      String no = rs.getString("mobile");
      String email = rs.getString("email");

      jLabel5.setText(JOB);
      jLabel16.setText(state);
      jLabel31.setText(no);
      jLabel7.setText(email);
    }

    while (rs2.next()) {
      String info = rs.getString("information");
      jTextArea1.setText(info);
    }

    con.close();
    st.close();
    rs.close();
    rs2.close();
  } catch (Exception e) {
    JOptionPane.showMessageDialog(null, "Error" + e.getMessage());
  }
}

Answer 1

在WHERE语句中，必须用单引号'包围实际值，以引用实际值。 MySQL文档第 9.1.1 String Literals章对此进行了说明。您的代码应为：

String P = "Select INFORMATION FROM pinfo where email = 'mil@gmail.com';";

如果您打算使用JDBC，请了解准备好的状态菜单。参见Using Prepared Statements。

Answer 2

您错过了电子邮件ID周围的单引号。请尝试以下

String S= "Select mobile,state,mobile,email,job from signup where email = 'mil@gmail.com';";

String P = "Select INFORMATION FROM pinfo where email = 'mil@gmail.com';";