SQLite with Android Studio, return all records selected by 2 arguments - sql

Question

let's assume that i have a table with columns such as:
ID SSID BSSID RSSI
1 abcd hs:hd:sd -60
2 abcd hs:hd:po -68
There are about 5000 records with the same SSID, slighltly different BSSID and the LEVEL values. My device is scanning the nearest environment for WiFi networks, therefore I know their MAC address and level of RSSI. I pick 3 with the highest value od RSSI.
First thing I would like to know if it is possible to search through the database to get all the records with the LEVEL value equal or close to 60, for instance 59,58,61.
Secondly, is there a way to query the database to return all the records with the same MAC addresses and RSSI values as from the 3 best scan result? If so, how would that query look like?
EDIT: Thanks for all the answers. What I'm trying to do now is to compare 3 scans with records stored in database with getRequiredData function. I would like to pass 2 parameters to this function, mac address and level and find records with same value for both parameters. The rawQuery seems to be fine, code is compiling but the app is crashing with the first scan. I cant find the cause of it, is it because my logic of getting these parameters is wrong or does it have something to do with query?
public Cursor getRequiredData(String mac, int level){
SQLiteDatabase db = this.getWritableDatabase();
Cursor res = db.rawQuery("SELECT BSSID, RSSI FROM TABLE_NAME WHERE BSSID =? AND RSSI=?", new String[] {mac, level});
return res;
}
scan part:
class WifiReceiver extends BroadcastReceiver {
#Override
public void onReceive(Context context, Intent intent) {
sb = new StringBuilder();
Comparator<ScanResult> comparator = new Comparator<ScanResult>() {
#Override
public int compare(ScanResult o1, ScanResult o2) {
return (o1.level>o2.level ? -1 : (o1.level==o2.level ? 0 : 1));
}
};
lista = wifiManager.getScanResults();
Collections.sort(lista, comparator);
for (int i = 0; i < lista.size(); i++) {
scanResult = wifiManager.getScanResults().get(i);
sb.append(new Integer(i + 1).toString() + ". " + (lista.get(i)).SSID + " " + (lista.get(i)).BSSID + " " + (lista.get(i)).level + "\n");
boolean isInserted = myDb.insertData(lista.get(i).SSID.toString(), lista.get(i).BSSID.toString(), lista.get(i).level);
if (isInserted = true)
Toast.makeText(MainActivity.this, "Data inserted", Toast.LENGTH_LONG).show();
else
Toast.makeText(MainActivity.this, "Data not inserted", Toast.LENGTH_LONG).show();
}
for (int i=0; i<4; i++)
{
scanResult = wifiManager.getScanResults().get(i);
match = myDb.getRequiredData(lista.get(i).BSSID.toString(), lista.get(i).level);
}
Log.i("match values: ", DatabaseUtils.dumpCursorToString(match));
txt.setText(sb);
wifiManager.startScan();
}
}
Here is what match contains:
2018-12-10 16:36:26.334 13347-13347/com.example.maciek.wifiscann I/match values:: >>>>> Dumping cursor android.database.sqlite.SQLiteCursor#e1a86d1
0 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
1 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
2 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
3 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
4 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
5 {
BSSID=f4:c5:ed:5c:s6:20
RSSI=-69
}
<<<<<

Answer 1

To get the 3 rows with the closest values to 60 in column LEVEL:
SELECT * FROM tablename ORDER BY ABS(LEVEL - 60), LEVEL LIMIT 3
For the 2nd part of your question, you should provide sample data of the table. Edit:
From the sample data that you posted I don't see a column RSSI, but if it exists in the table then the SELECT statement is ok.
Change the 2nd parameter of rawQuery() to:
new String[] {mac, String.valueOf(level)}
because level is int.
In onReceive() you use myDb. I don't know how you initialize it.
If the app crashes you must copy the log, the part that identifies the problem and post it.

Answer 2

First thing I would like to know if it is possible to search through
the database to get all the records with the LEVEL value equal or
close to 60, for instance 59,58,61.
SELECT * FROM your_table WHERE level BETWEEN 59 AND 61;
where your_table is the respective table name.
Note if levels are negative (as per example data) then BETWEEN requires the lowest value first so it would be BETWEEN -61 AND -59.
Secondly, is there a way to query the database to return all the
records with the same MAC addresses and RSSI values as from the 3 best
scan result? If so, how would that query look like?
SELECT * FROM your_table WHERE your_mac_address_column = 'the_mac_address_value' AND RSSI = 'the_rssi_value' ORDER BY LEVEL DESC LIMIT 3
Note the above assumes that the MAC address is stored in a column (if NOT then cannot be done unless the mac address can be correlated to a column).
Assumes best LEVEL is lowest so -1 is better than -60 (if not then use ASC instead of DESC)
Again your_table, your_mac_address_column, the_mac_address_value and the_rssi_value would be replaced accordingly with actual values (note that strings should be in single quotes).