Am I Properly Using JSON Files with $.getJSON?

Am I Properly Using JSON Files with $.getJSON?

I just got introduced to JQuery and using JSON data yesterday. I'm wondering if I'm properly and efficiently using them because it's really not making sense. 

With what I have to work with, It seems like I'm grabbing entire databases worth of data EVERY time someone makes a request and processing it in the browser. That doesn't seem remotely efficient, why can't I just ask for the piece of data I need by querying the JSON file for items that match certain criteria, allowing the server to do most of the work? 

We have a site using ASP.NET (aspx files using C#, that's about all I know). 

We have numerous databases that we can access as either JSON or XML. 

The many databases are linked together with ID's, I need to be able to search each database for a specific ID and pull out all the specific information related to that ID and throw it into a multidimensional array. Can I do this without grabbing every single DB we have, loading it into the browser and manipulating it with JavaScript? Some DB's are over 2MB in size, I feel like it could get sluggish quickly. 

Here's the code I'm currently using, part of it anyway. I'm not happy with this either, why do I have to chain my $.getJSON requests together with functions? If I don't, the array's don't get built because the $.getJSON happens simultaneously as any outside methods I use to manipulate the array. 
(JQuery 1.5.1)

  2. var elem1Array = new Array();
  3. var elem2Array = new Array();


  6. function assessElem1()
  7. {
  8. $.getJSON('http://XXX.XXX.XXX.svc/TableName1?$format=json&$callback=?', 
  9. function (response) 
  10. { 
  12. $.each(response.d, function (index, value)
  13. {
  14. elem1Array.push(value.ID);
  15. //alert(newArray[index]);
  16. });
  17. assessElem2(elem1Array);
  18. }

  20. ); 
  21. }
  23. function assessElem2(Array1)
  24. {
  25. $.getJSON('http://XXX.XXX.XXX.svc/TableName2?$format=json&$callback=?', 
  26. function (response) 
  27. { 
  29. $.each(response.d, function (index, value)
  30. {
  31. elem2Array.push(value.ID);
  32. //alert(newArray[index]);
  33. });
  34. groupObjects(elem1Array,elem2Array);
  35. }

  37. ); 
  39. }

  41. function groupObject(array1,array2)
  42. {
  43.       // This function will search for matching ID #'s and create a
  44.       // multimensional array with the parent ID and the ID's of the
  45.       // matching child elements. 
  46. }
It's possible for me to create and use a .aspx file instead but I don't know much about C# or if it would be any more efficient than JQuery.