I reinvented the wheel of course...

Before I knew what a database was and that there was this thing called SQL I had the problem at work where I had to manually parse, filter, and cross reference very large data sets every week that were presented to me as massive very slow to load spreadsheets. Having some very old and dusty coding ability I hadn't used since college (I became an electronics hardware engineer) and annoyed by the time consuming manual process of going through the spreadsheets, I decided to try to automate it.

A colleague who had previously worked for IBM long ago suggested I learn Perl to try to do it (he said a lot of his coworkers at IBM used Perl). I bought a copy of Learning Perl, spent my free time at work going through it, and once finished basically wrote a rudimentary database tool (I just didn't know it at the time) that extracted all/only the relevant columns from each data set, used hashes to give each row of each dataset a "primary key" via the hash key, and more or less wrote some basic core Perl to do what I later learned SQL and an actual database could do a lot more efficiently given the size of the datasets.

I don't regret it though, it lead to me using Perl for lots, and lots, and LOTs, of other very cool things. At my peak Perl usage, I once was able to use it to extract millions of storage locations/part numbers/inventory counts from our central database, decode (they followed a complex but consistent algorithm) the locations in to exact physical coordinates and storage location dimensions within our warehouse, and modify the files (fortunately human readable) used by my company's expensive warehouse motion simulation tool to automatically draw all our pallet racking, shelving, etc. in the proper physical location, to scale, with an inventory snapshot of any given day requested for ultimate use in the active simulation tool.

As merely a "dabbler" in coding/computer science, I would have never thought I would ever be capable of something like that, but that's what Perl enabled me to do... in my own hackish, workaround way. :-)