the limit clause should be "10,20" with no space between the coma and the 20.
public Cursor getAllDiscounts() {
return db.query(DATABASE_TABLE, new String[] { KEY_ROWID,
KEY_PORTALNAME, KEY_TITLE, KEY_TITLESHORT, KEY_DEALURL,
KEY_ENDDATE, KEY_COORDS, KEY_CITY, KEY_IMAGEDEAL,
KEY_CLICKPRICE, KEY_CONVERSIONPERCENTAGE, KEY_FINALPRICE,
KEY_ORIGINALPRICE, KEY_SALES, KEY_KATEGORIJA, KEY_POPUST },
null, null, null, null, null, "10,20");
}