Connected Textures

I was wondering how you can get connected textures, well I think that's what you'd call it, I want to make a table, so when you place it down 1 by 1, the block has all 4 legs, but if you make it 2 by 1 or 1 by 2, one block has two legs and the otehr has the other 2 legs or you can make it2 by 2 and each block will have a single lesg, and if you make it 2 by 3, or 3 by 3, the blocks in the middle will only be the top part without legs exept for the corners.

Thanks if you understand! :)