当一个表的数据库中不存在行时如何插入记录

Question

我正在尝试插入新记录，并同时检查记录是否存在。但是查询无法显示该功能，请给我建议。 当应用程序运行时，它显示失败（无法插入数据。注册失败。）此消息来自Java文件。我想在已插入的应用程序记录中显示消息，或者记录存在。

//java file
           public class SignupActivity extends AsyncTask<String, Void, String> {

                            private Context context;

                            public SignupActivity(Context context) {
                                this.context = context;
                            }

                            protected void onPreExecute() {

                            }

                            @Override
                            protected String doInBackground(String... arg0) {
                                String fullName = arg0[0];
                              //  String userName = arg0[1];
                                String passWord = arg0[1];
                                String phoneNumber = arg0[2];
                                String emailAddress = arg0[3];

                                String link;
                                String data;
                                BufferedReader bufferedReader;
                                String result;

                                try {
                                    data = "?fullname=" + URLEncoder.encode(fullName, "UTF-8");
                                //    data += "&username=" + URLEncoder.encode(userName, "UTF-8");
                                    data += "&password=" + URLEncoder.encode(passWord, "UTF-8");
                                    data += "&phonenumber=" + URLEncoder.encode(phoneNumber, "UTF-8");
                                    data += "&emailaddress=" + URLEncoder.encode(emailAddress, "UTF-8");

link = "http://mydoamin.com/mangoair10/tryrr.php" + data;
                        URL url = new URL(link);
                                    HttpURLConnection con = (HttpURLConnection) url.openConnection();

                                    bufferedReader = new BufferedReader(new InputStreamReader(con.getInputStream()));
                                    result = bufferedReader.readLine();
                                    return result;
                                } catch (Exception e) {
                                    return new String("Exception: " + e.getMessage());
                                }
                            }
                         @Override
                            protected void onPostExecute(String result) {
                                String jsonStr = result;
                                if (jsonStr != null) {
                                    try {
                                        JSONObject jsonObj = new JSONObject(jsonStr);
                                        String query_result = jsonObj.getString("query_result");
                                        if (query_result.equals("SUCCESS")) {
                                            Toast.makeText(context, "Data inserted successfully. Signup successfull.", Toast.LENGTH_LONG).show();

                                        } else if (query_result.equals("FAILURE")) {
                                            Toast.makeText(context, "Data could not be inserted. Signup failed.", Toast.LENGTH_SHORT).show();

                                        }
                                        else {
                                            Toast.makeText(context, "Couldn't connect to remote database.", Toast.LENGTH_SHORT).show();
                                        }
                                    } catch (JSONException e) {
                                        e.printStackTrace();
                                       // Toast.makeText(context, "Error parsing JSON Please data Fill all the records.", Toast.LENGTH_SHORT).show();
                                        Toast.makeText(context, "Please LogIn", Toast.LENGTH_SHORT).show();

                                    }
                                } else {
                                    Toast.makeText(context, "Couldn't get any JSON data.", Toast.LENGTH_SHORT).show();
                                }
                            }
                        }

                        //php file
                        <?php
                        $con=mysqli_connect("localhost","user","password","database");
                        if (mysqli_connect_errno($con))
                        {
                           echo '{"query_result":"ERROR"}';
                        }

                        $fullName = $_GET['fullname'];
                        //$userName = $_GET['username'];
                        $passWord = $_GET['password'];
                        $phoneNumber = $_GET['phonenumber'];
                        $emailAddress = $_GET['emailaddress'];

         $sql = "INSERT INTO users10 (fullname,password,phone,email)
                        SELECT * FROM (SELECT '$fullName', '$passWord', '$phoneNumber','$emailAddress') AS tmp
                        WHERE NOT EXISTS (
                            SELECT name FROM users10 WHERE phone = '$phoneNumber' OR email='$emailAddress'
                        ) LIMIT 1 ";

                        $result=mysqli_query($con,$sql);

                        if($result == true)
                        {
                                            echo '{"query_result":"SUCCESS"}';
                                        }else{
                                            echo '{"query_result":"FAILURE"}';
                        }
                        mysqli_close($con);
                        ?>

Answer 1

我认为您需要“在重复的密钥更新上”

这将更新给定记录（如果存在），但如果没有则插入新记录。

在重复键上

Answer 2

正如@ali已经说过的，您需要检查用户是否存在，然后继续创建它：

/* Connect to the DB using MySQLi class */
$mysql = new mysqli('localhost', 'user', 'password', 'database');    

/* If an error code is reported... */
if($mysql->connect_errno)
{
  echo json_encode(array(
    'query_result' => 'ERROR'
  ));
}
/* Otherwise go ahead... */
else
{
  /* Prepare a select statement to check user existence */
  $selectStmt = $mysql->prepare("SELECT * FROM `users10` WHERE `phone` = ? OR `email` = ?");

  /* Retrieve arguments */
  $fullName = $_GET['fullname'];
  //$userName = $_GET['username'];
  $passWord = $_GET['password'];
  $phoneNumber = $_GET['phonenumber'];
  $emailAddress = $_GET['emailaddress'];

  /* Binding parameters */
  $selectStmt->bind_param('ss', $phoneNumber, $emailAddress);

  /* Execute statement */
  if (!$selectStmt->execute()) {
    echo json_encode(array(
      'query_result' => 'ERROR'
    ));
  }
  else
  {
    /* If the number of returned rows is 0 */
    if(0 === $selectStmt->get_result()->num_rows)
    {
      $insertStmt = $mysql->prepare("INSERT INTO `users10` (`fullname`, `password`, `phone`, `email`) VALUES (?, ?, ?, ?)");
      $insertStmt->bind_param('ssss', $fullName, $passWord, $phoneNumber, $emailAddress);

      /* Try to insert the new user */
      if (!$insertStmt->execute()) {
        echo json_encode(array(
          'query_result' => 'FAILURE'
        ));
      }
      else
      {
        echo json_encode(array(
          'query_result' => 'SUCCESS'
        ));
      }
    }
    else
    {
      echo json_encode(array(
        'query_result' => 'FAILURE'
      ));
    }
  }
}