Conventional cocktail book indexes are poor substitutions for databases, because in very of few of them can you look up a drink by ingredient. And when you can, it's only by base ingredient- gin, vodka, etc., instead of the mixer or modifier. I often want to look up drinks with ingredients like grapefruit juice or Creme Yvette, so this doesn't help.
Most online drink databases, on the other hand, are easily searchable but have too many drinks and no credits attached to the recipes. So you get 300 versions of the drink but don't know if someone just made it up or if it comes from a reliable source.
In one case, anyway, there is a good solution. All the recipes from the Savoy Cocktail Book can be found in a very simple searchable database here. We owe this to the efforts of Jimmy Patrick- bartender, blogger, and apparently secret programmer, and to Erik Ellestad who scanned in the whole book in order to work on his Savoy Cocktail Project.
Unlike most drink books, the Savoy has wonderful illustrations throughout the text that make it a must-own for all serious cocktailians. I don't feel guilty sharing it, as this database is more of a searchable accompaniment to the beautiful hard copy, which you can find in reprint.
What would be cool for modern cocktail books is if they had online searchable databases that didn't necessarily return the whole recipe, but told us the page number that the drinks were on so we could look them up in our hard copy. That would combine the convenience of a database without any income loss for the author. Hmmm, project!