ORDER BY not using index?

Hi, Can someone perhaps assist with the below... I'm not sure at all why my index aren't being used for the ORDER BY. Currently some 443K records in the table, but this will grow to a good few million. I simply cannot, afford a filesort. mysql SELECT COUNT(*) FROM myTable; +--+ |

Re: ORDER BY not using index?

Hi, Your query have to access all rows in `myTable`, thus MySQL optimizer guesses reading sequentially is faster than working through an index. http://dev.mysql.com/doc/refman/5.6/en/mysql-indexes.html The case of not using index, * Reading whole myTable.MYD sequentially * Sorting 443k rows