Can i fill a dropdown with data from a database or a Json file?

I'm assuming you are using the new UI elements and canvas?

This is simple:

 public Dropdown myDropdown; // Make sure to assign this
 private List<string> data;
 
 void Start()
 {
      data = LoadDataFromDBOrJSON(); // Or whatever way you will read your data in
 
      myDropdown.options.Clear();
      foreach(string str in data)
      {
         myDropdown.options.Add(new Dropdown.OptionData(str));
     }
 }

The same question cómo leer los datos del mysql db ??,Lo mismo que pregunto tsondhi2006 cómo leer los datos del mysql db ??

Did it:-

1) Create a c# file

 void Func1()
     {        
         WWW www = new WWW ("127.0.0.1/somefolder/somefile.php");// give location of Php file
         while (!www.isDone) {
         }
         string itemsDataString = www.text;
         string[] wwwItems = itemsDataString.Split (';'); //the values in mysql db is picked in a single string and should have some marker so as to split
         DD.options.Clear ();
         foreach (string str in wwwItems) {
             DD.options.Add (new Dropdown.OptionData (str));
         }
 }

2) Create a php file which will pass the values from mysql to unity [somefile.php]:-

 <?php
     $conn = new mysqli("127.0.0.1", "root", "", "somedb");
 
     if ($conn->connect_error) {
        die("Connection failed: " . $conn->connect_error);
     }
     $sql = "SELECT * FROM sometable";
     $result = $conn->query($sql);
     if ($result->num_rows > 0) {
         // output data of each row
             while($row = $result->fetch_assoc()) {
             echo ";".$row["somefield"];
         }
     }
     $conn->close();
 ?>