$.getJSON returns only one entry

Hell seeing as everyone is repeating themselves thought id get in on the action.

As @RoyMcCrosan said your data value is an array, however your myJson variable is an object. What you doing is looping through the array an placing each cell in that array into the myJson variable, (here's the important bit), overwriting the value before it. So you end up with only the last value in the array.

Now without knowing what you want to do with the data we can't really say what you should do but here's a few common cases ive had to do:

If you want to simply copy the data and work with it else where as an array simply scrap the $.each

var myJson = [];
$.getJSON(url, function(data) {
    myJson = data;
    console.log(myJson);
});

If you want to map the data to end up with an array but in a different format:

var myJson = [];
$.getJSON(url, function(data) {
    myJson = data.map(function (d) {
      return {}; //Some modified object
    });
    console.log(myJson);
});

If you want to iterate the array and extract a property from each object to add to you myJson variable;

var myJson = {};
$.getJSON(url, function(data) {
    data.forEach(function (d) {
       //Some logic for figuring property name.
       var i = 'FieldName';
       myJson[i] = d[i];
    });
    console.log(myJson);
});

Finally as data is an array using native looping methods such as .forEach or a for loop. They will be faster then $.each. Also technically myJson is not JSON its a JavaScript object in its own right.