Nice effort on an interesting topic. However, the book could use a better technical review. For example the first recipe will not work as expected with out a m

Nice effort on an interesting topic. However, the book could use a better technical review. For example the first recipe will not work as expected with out a multi-column unique index (specifically the MySql example). I feel that the preexisting knowledge required for such examples does not align with the stated target audience for the book.