Question

I have a database with the columns: id, pdate, pvalue1, pvalue2. First I make a query with a cursor:

Cursor c = ourDatabase.query(DATABASE_TABLE, new String[] { "_id","pdate","pvalue1","pvalue2"},
                    "pdate >= ? AND pdate <= ?",  new String[] { datefrom, dateto }, null, null, null);   

This gives me some rows, for example if pdate = 20120318, then pvalue1 = 58, pvalue2=29. These are strings so I can give a value of “XX” to pvalue2. I would like to sum the pvalue1 between the given datefrom and dateto and group them by pdate where pvalue2 = XX. My problem is that I cannot put this condition into the query (with that its working, like “pvalue2 = XX”..), because I need the other datas too.

if (c.moveToFirst())
{
     do{
         if (c.getString(3).equals("XX")){
         Log.i("XX", c.getString(1) + " " + c.getString(2)) + " " + c.getString(3));

          }
         else {
         Log.i("NotXX",  c.getString(1) + " " + c.getString(2)) + " " + c.getString(3));

          }

     while (c.moveToNext());
     }
}

It is okay so far, so I can log the datas with this where pvalue2 = XX and NotXX and get something like this:
(pdate,pvalue1,pvalue2) 20120317,48,29;——;20120317,21,54;——-20120317,11,XX;—–20120318,79,71;——-20120318,21,XX;

What I would like to do?

First: Grouping the sums (pvalue1) by pdate and indicate it if pvalue2 is XX or notXX, so somethnig like this:
20120317,NotXX,69 (since 48+21=69) ——– 20120317,XX,11 ——– 20120318,NotXX,79 ——– 20120318,XX,21

After this I would like to substract the XX sum from the NotXX sum for every day. I would like to get:
20120317,58 (since 69-11) ——- 20120318,58 (since 79-21)

How sould I do this?
Thank you very much in advance!

Answer 1

My problem is that I cannot put this condition into the query

You are probably wrong. You can add something like (syntax may contain errors)

“select sum(select pdate from DATABASE_TABLE where pdata > x and pdate < y) as sum”

to the projection argument and you get that result as a column named sum. The only problem is that there is no support for ? in projection (at least I have not tried it but I guess it would not work)

If that’s not what you want then there is very likely a different way. SQLite is very powerful.

Edit:

Would that be what you want? It’s not done in SQL but it would print the sum you want for each day.

Cursor c = ourDatabase.query(DATABASE_TABLE, new String[] { "_id","pdate","pvalue1","pvalue2"},
        "pdate >= ? AND pdate <= ?",  new String[] { datefrom, dateto }, null, null, "pdate");
boolean first = true;
if (c != null) {
    String currentDate = null;
    int sum = 0;
    while (c.moveToNext()) {
        String date = c.getString(1);
        int value1 = c.getInt(2);
        String value2 = c.getString(3);
        if (!date.equals(currentDate)) {
            if (!first) {
                Log.d("TAG", "The result for " + currentDate + " is: " + sum);
            } else {
                Log.d("TAG", "Date has changed, but we don't have data yet.");
            }
            first = false;
            currentDate = date;
            sum = 0;
        }
        if ("XX".equals(value2)) {
            Log.d("TAG", "new line: " + date + ", " + value1 + ", " + value2 + " -");
            sum -= value1;
        } else {
            Log.d("TAG", "new line: " + date + ", " + value1 + ", " + value2 + " +");
            sum += value1;
        }
    }
    if (!first) {
        Log.d("TAG", "The last result: " + currentDate + " is: " + sum);
    }
    c.close();
}

Edit2: This might work when you want it done by the database.

Cursor c = ourDatabase.rawQuery(
        "SELECT pdate, sum(sum2) AS sum1 FROM " +
        "(" +
        "   SELECT pdate, pvalue1, pvalue2, -sum(pvalue1) AS sum2 " +
        "      FROM " + DATABASE_TABLE +
        "      WHERE pvalue2='XX' GROUP BY pdate" +
        "   UNION " +
        "   SELECT pdate, pvalue1, pvalue2, sum(pvalue1) AS sum2 " +
        "      FROM " + DATABASE_TABLE + 
        "      WHERE pvalue2!='XX' GROUP BY pdate" +
        ") " +
        "   WHERE pdate>=? AND pdate<=? " +
        "   GROUP BY pdate",
        new String[] { datefrom, dateto });
if (c != null) {
    while (c.moveToNext()) {
        String date = c.getString(0);
        int value1 = c.getInt(1);
        Log.d("TAG", "The result for " + date + " is: " + value1);
    }
    c.close();
}