How to synchronize data between flutter app (SQFLite) and a MySQL server database?

[Mohamed Yanis]

Hello,

I have a backend server i.e. I have an external MySQL database (localhost) that contains a "questions" table characterized by their level (Easy, Medium, Hard) and their class(1st class, 2nd class, 3rd class).

I have an internal database (SQFLite) that contains a "students" table with level and class attributes that contain in the external MySQL database.

I want to post only the questions that correspond to the level and class of the student that is already added in the internal database "SQFLite".

I posted all the questions in the JSON form but did not match the level and class of the student currently added, But I want when I add a new student with their level and class in the internal database"SQFLite", the questions that are displayed must be matched to that of the student.

Code Link: https://stackoverflow.com/questions/63314232/how-to-synchronize-data-between-flutter-app-sqflite-and-a-mysql-server-databas

[Suzuki Tomohiro]

I felt that you know what to do. Match student’s level (SQFLite) when fetching questions in MySQL.

What is the challenge for you?

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[Souvik Dutta]

Yes you can do a normal query and have the required data.

Souvik flutter dev

[Mohamed Yanis]

I want to post only the questions that correspond to the level and class of the student that is already added in the internal database "SQFLite".

I posted all the questions in the JSON form but did not match the level and class of the student(Displaying all questions), But I want when I add a new student with their level and class in the internal database"SQFLite", the questions that are displayed must be matched to that of the student.

Le samedi 8 août 2020 14:35:46 UTC+2, Suzuki Tomohiro a écrit :

I felt that you know what to do. Match student’s level (SQFLite) when fetching questions in MySQL.

What is the challenge for you?

On Sat, Aug 8, 2020 at 07:26 Mohamed Yanis <mmoham...@gmail.com> wrote:

Hello,

I have a backend server i.e. I have an external MySQL database (localhost) that contains a "questions" table characterized by their level (Easy, Medium, Hard) and their class(1st class, 2nd class, 3rd class).

I have an internal database (SQFLite) that contains a "students" table with level and class attributes that contain in the external MySQL database.

I want to post only the questions that correspond to the level and class of the student that is already added in the internal database "SQFLite".

I posted all the questions in the JSON form but did not match the level and class of the student currently added, But I want when I add a new student with their level and class in the internal database"SQFLite", the questions that are displayed must be matched to that of the student.

Code Link: https://stackoverflow.com/questions/63314232/how-to-synchronize-data-between-flutter-app-sqflite-and-a-mysql-server-databas

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[Souvik Dutta]

You can query the questions, then extract the level and class info and use this extracted info to match with the students level and class. Then you can use this matched data to create a new list or json object that you can then show to the user. Hope this helps.

Souvik flutter dev

On Sat, Aug 8, 2020, 8:52 PM Mohamed Yanis <mmoham...@gmail.com> wrote:

I want to post only the questions that correspond to the level and class of the student that is already added in the internal database "SQFLite".

I posted all the questions in the JSON form but did not match the level and class of the student(Displaying all questions), But I want when I add a new student with their level and class in the internal database"SQFLite", the questions that are displayed must be matched to that of the student.

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[Mohamed Yanis]

I know the idea, but I don't know how he does it. Can You Help Me :)

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[Suzuki Tomohiro]

Hi Mohamed,

Do you know how to query SQFLite?

Do you know how to query MySQL?

Do you know how to exchange data between Flutter app and your backend server using HTTP?

On Sat, Aug 8, 2020 at 11:22 Mohamed Yanis <mmoham...@gmail.com> wrote:

I want to post only the questions that correspond to the level and class of the student that is already added in the internal database "SQFLite".

I posted all the questions in the JSON form but did not match the level and class of the student(Displaying all questions), But I want when I add a new student with their level and class in the internal database"SQFLite", the questions that are displayed must be matched to that of the student.

Le samedi 8 août 2020 13:26:16 UTC+2, Mohamed Yanis a écrit :

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[Mohamed Yanis]

Yes, I know how to query SQFLite and MySQL, but I don't know how to exchange data between Flutter application and your backend server using HTTP?

My problem is in the display of the questions which are all displayed, and they are not dependent on the level and the class of the student

[Souvik Dutta]

Suppose A contains the SQFlite data and B contains the level/class of the student

Then you can do

C = []; // container for the required data

for (var a = 0; a <length(A); a++){

    if (A[a].level == B.level){

        C.append(A[a]);

    }

}

Now you can show the data in C. I guess you can morph this to suite your requirement. 

Souvik flutter dev

[Mohamed Yanis]

hi Souvik Dutta,

I did not understand where to put this code :)

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[Souvik Dutta]

Wherever you want to check for the level before adding the questions. Are you new to flutter?👋😀

Souvik flutter dev

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[Suzuki Tomohiro]

> I don't know how to exchange data between Flutter application and your backend server using HTTP

Good. Then learn this. 

https://flutter.dev/docs/cookbook/networking/fetch-data

[Suzuki Tomohiro]

Send SQFLite data to your backend server.

The backend server saves the data to MySQL.

On Sun, Aug 9, 2020 at 07:33 Mohamed Yanis <mmoham...@gmail.com> wrote:

Hi Suzuki ,

It's good I already did but the problem is not there,the problem is how to synchronize between the data of the student (their level, their class) "SQFLite" and the data of Mysql ( level, class)

[Suzuki Tomohiro]

How: use HTTP post method. JSON format is a nice choice to encode the data.

On Sun, Aug 9, 2020 at 09:10 Mohamed Yanis <mmoham...@gmail.com> wrote:

Please, Why and How to send QFlite data to the Mysql server?

[Suzuki Tomohiro]

Your Flutter code is using HTTP “GET”, not “POST”. You flutter code is not sending any data to your PHP backend server.

Learn “HTTP GET parameter” or “HTTP POST” to send data from your Flutter code to your server. Google the keywords.

On Sun, Aug 9, 2020 at 09:42 Mohamed Yanis <mmoham...@gmail.com> wrote:

I used it, can you consult this link :  https://stackoverflow.com/questions/63318698/how-to-match-student-s-level-student-s-class-sqflite-when-fetching-questions-i

[Suzuki Tomohiro]

Yes, I know. HTTP POST method can get data from the server.

On Sun, Aug 9, 2020 at 14:33 Mohamed Yanis <mmoham...@gmail.com> wrote:

But, I want to get data (questions) from MySQL database Not Post it!

[Suzuki Tomohiro]

Then learn this. https://flutter.dev/docs/cookbook/networking/fetch-data

On Tue, Aug 11, 2020 at 04:08 Mohamed Yanis <mmoham...@gmail.com> wrote:

unfortunately, I did not understand, and I do not know how to do it?

[Suzuki Tomohiro]

Specify an HTTP POST or GET parameter for the level of questions.

On Tue, Aug 11, 2020 at 09:26 Mohamed Yanis <mmoham...@gmail.com> wrote:

Hi, Suzuki

the user is a student. who must complete the form on the mobile app (SQFLite) which contains their name, level, and class. 

As soon as it is added, only the questions (Get it from MySQL) that correspond to their level should be displayed and their class is not the questions of all levels .

I edited the code in Stackoverflow 

THE PROBLEM :

display of all questions of all levels and classes without depending on the student added.

[Suzuki Tomohiro]

Nice, it’s getting closer. I’m expecting something like this for the URL:

http://10.0.2.2/Try/Try.php/?level=Easy

On Tue, Aug 11, 2020 at 10:23 Mohamed Yanis <mmoham...@gmail.com> wrote:

do we specify a parameter for the level like this :

  getMethod()async{
    String theUrl = 'http://10.0.2.2/Try/Try.php/?idlevel';
    var res = await http.get(Uri.encodeFull(theUrl),headers:{"Accept":"application/json"});
    var responsBody = json.decode(res.body);
    return responsBody;
  }

if the parameter specification for the level is not like this tell me how to do it?

[Mohamed Yanis]

Thanks,but it doesn't work.

 it's my PHP code :

``` 

<?php
header("Content-type: application/json; charset=utf-8");
try{
$conn = new PDO('mysql:host=localhost;dbname=relations;charset=utf8','root','');
$conn ->setAttribute(PDO::ATTR_ERRMODE,PDO::ERRMODE_EXCEPTION);
}
catch(PDOException $exc){
    echo $exc->getMessage();
    die("could not connect");
}
?>
<?php
$makeQuery ="SELECT * FROM questions ";
$stamement = $conn-> prepare($makeQuery);
$stamement -> execute();
$myarray = array();
while ($resultsFrom = $stamement->fetch()){
    array_push(
        $myarray,array(
        "idques"=>intval($resultsFrom['idques']),
        "description"=>$resultsFrom['description']
        )
    );
}
echo json_encode($myarray);
?>
```

[Suzuki Tomohiro]

Can you check why your PHP code does not work?

[Suzuki Tomohiro]

No, your PHP code have to return the questions that match the level.

On Wed, Aug 12, 2020 at 12:20 Mohamed Yanis <mmoham...@gmail.com> wrote:

my PHP code is working normally.
But it still displays all questions and does not display questions that match the level and class of the student.

what do I have to do?

[Suzuki Tomohiro]

Your PHP code is also responsible for  "display all questions"

On Wed, Aug 12, 2020 at 12:43 Mohamed Yanis <mmoham...@gmail.com> wrote:

I modified my request in the PHP code to this one:
"SELECT * FROM questions where level =? & class=?"
  instead of :

"SELECT * FROM questions",

but there remains the same problem "display all questions"?

[Suzuki Tomohiro]

Pass level parameter when you need questions of a specific level. When you need all questions, then your Flutter app do not need the parameter.

On Thu, Aug 13, 2020 at 03:29 Mohamed Yanis <mmoham...@gmail.com> wrote:

Hi, Is the problem in requesting PHP code? if yes tell me what should I change ?

[Suzuki Tomohiro]

Yes, you need to change the query.

On Thu, Aug 13, 2020 at 10:30 Mohamed Yanis <mmoham...@gmail.com> wrote:

I did, but it didn't work
here is the request which we write in the PHP file: "SELECT * FROM questions where level=?"

Is there a change in the query?

[Suzuki Tomohiro]

No, I don’t. Learn if-statement in PHP to change the query based on the presence of a parameter value.

On Fri, Aug 14, 2020 at 09:59 Mohamed Yanis <mmoham...@gmail.com> wrote:

Hi Suzuki,

Please, Can you correct my query?

 "SELECT * FROM questions where level=?"  

[Mohamed Yanis]

Ok, thanks.