I use SQL, or something like it, on pretty much any project that needs to store any significant amount of data. Easily the most bang for my buck out of any of t

I use SQL, or something like it, on pretty much any project that needs to store any significant amount of data. Easily the most bang for my buck out of any of the skills I picked up in high school. Even if it's not SQL proper, you should learn a query language of some sort and get used to the idea of asking an engine to help you sort and filter your data in a consistent way. Once you have that mental model down, you'll find you can migrate between the SQL-likes and the SQL-not-so-likes comfortably, and pick the best tool for the job at hand.