B-tree or Bitmap

Recently I read a lot about databases, mostly theory but also from the design point of view. I have to admit that until recently I had no idea what a B-tree is. I mean beside that it is a kind of a data structure, but how it is build and why on average there is ...

No Duplicates in Subset

Yesterday I was helping a friend of mine with an interesting problem. There is a big table ~4MLN rows, it is wide (has many columns, lets say 30). We are interested in getting rows, which contain duplicates in 5 columns, we do not care what data are in other columns, at least not with regard ...

Speed-up VBA in Excel

There are various means of adding some speed to your VBA code. Probably not the most obvious one, but try to keep track of types of variables, define them explicitly. There is an option, which you put at the beginning of the file which will help you with it Option Explicit Moreover, there are different ...