How to obtain a certain data from an external sql database? - php

Question

I'd like to get data from an external database the fastest way. My problem is that I can make the query and get all the data then using JSON I am able to obtain what I need. But I am curious if there is a faster solution, so I go over all the data in the php, then find the appropriate data I need and returning ONLY it to the JSON instead of the whole query. The first solution might be slow when I need hunderds of records out of one million.
This would be the .php code looking for the username in case of an ID. How can I give that ID to the .php script?
$ID = $_GET['ID'];
try {
$stmt = $conn->prepare("SELECT USERNAME FROM APPUSERS WHERE ID=?");
$stmt -> execute(array($id));
while($row = $stmt->fetchAll(PDO::FETCH_ASSOC)) {
$userdata[] = $row;
}
$response = '1';
} catch(PDOException $e) {
echo 'ERROR: ' . $e->getMessage();
$response = '0';
}
print(json_encode($userdata));
If I remove the WHERE part of the sql code I can get all records in the table with the following code:
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://www.mywebpage.com/query.php");
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}
//convert response to string
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
Bresult=sb.toString();
}catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
Then from this Bresult variable I get retrieve the appropriate record e.g.
JSONArray jArray = new JSONArray(ViewPagerActivity.Bresult);
for(int i=0;i<jArray.length();i++){
JSONObject jsonObject = innerJsonArray.getJSONObject(j);
if (jsonObject.getString("ID").equals("12345") {
String user = jsonObject.getString("USERNAME");
}
}
So I go through all the records then retrieve the username I need.
However, I think this can be made faster if I can retrieve only the username I need and not all the records. The question is, how I can do it?
Thank you in advance!!