sum of numbers for a given column in a sqlite database - android-sqlite

Question

I am trying to get the sum of similar items in my rows in sqlite.
For example, all the values of x,all the values for y and all the values for z. I know how to use the WHERE clause in my query but the problem with it is that it requires i compare the values to another parameter. For example a query like this:
select sum(number_column) from your_table where number_column = 'some_number'
From the above, i dont have 'some_number' to compare to. So i need a way to add all the values for each similar rows, kind of like grouping them together.
So i would end up with something like:
x 25
y 24
z 16
Is this possible? Any suggestions are welcomed.
EDIT:
I tried this after Cristian's suggestion:
private void getSumOfGroupedTime() {
SQLiteDatabase db = this.getReadableDatabase();
Cursor c = db.rawQuery("SELECT " + KEY_CREATED_AT_AM_PM + ",sum(quantity) as sum FROM " + TABLE_SALES
+ " GROUP BY " + KEY_CREATED_AT_AM_PM, null);
c.moveToFirst();
double i = c.getDouble(0);
Log.d("sum_values_", String.valueOf(i));
c.close();
}
But it returns 1 for the three similar items i added in which each of these items have 1 as quantity. I expected 3. I'm i doing it wrong?

Answer 1

Assuming you have a table that has the following structure:
+----------------+--------+
| KEY_CREATED_AT | number |
+----------------+--------+
| a | 132 |
| e | 264 |
| f | 142 |
| x | 132 |
| y | 122 |
| z | 112 |
+----------------+--------+
In order to have the sum of these separate values you would use the clause group by
So the query would be like this:
SELECT KEY_CREATED_AT,sum(number) as sum FROM table_name
GROUP BY KEY_CREATED_AT
Example here: sqlfiddle
private void getSumOfGroupedTime() {
SQLiteDatabase db = this.getReadableDatabase();
Cursor c = db.rawQuery("SELECT " + KEY_CREATED_AT_AM_PM + ",sum(quantity) as sum FROM " + TABLE_SALES
+ " GROUP BY " + KEY_CREATED_AT_AM_PM, null);
try {
while (c.moveToNext()) {
Double sum = c.getDouble(1);
Log.d("Sum is: " + sum);
}
} finally {
c.close();
}
}