how to get count column

问题:

I'd like to get the value of Count column from cursor.

public Cursor getRCount(String iplace) throws SQLException
{
 try {
      String strSql = "SELECT COUNT(_id) AS RCount FROM tbName WHERE place= '" + iplace + "'";            
      return db.rawQuery(strSql, null);
    } catch (SQLException e) {
        Log.e("Exception on query", e.toString());
        return null;
    }
} 

I tried to get this count column value from cursor like below

Cursor cR = mDbHelper.getRCount(cplace);if (cR.getCount() > 0){long lCount = cR.getLong(0);}cR.close();}

I got the debug error. How to get it?

PS: Could I use nested cursors?

回答1:

You should use DatabaseUtils.longForQuery utility method to run the query on the db and return the value in the first column of the first row.

int sometotal=DatabaseUtils.longForQuery(db,"SELECT COUNT(_id) AS RCount FROM tbName WHERE place= '" + iplace + "'",null);

回答2:

The Cursor is positioned before the first row when you get it back from rawQuery(). Call moveToFirst() before attempting to use the Cursor, and your problem should go away.