I run into a need for this type of software frequently but I don't know what it's called or if it exists. I am very adept at Google Sheets and it works great for pulling in data from other places, creating custom little dashboards and forms, etc but where it's not particularly good is storing relational data for example "This book is written by author" and then having "author" be some other entity with its own attributes.

Now of course, there's SQL but using SQL requires learning SQL syntax which is much more complex. Plus, you have to define a schema and changing schema after you've made the db can be complicated. Not to mention if you use SQL, now you need some kind of front-end to the SQL to make it more friendly to a user even if they would be fine at their skill level managing google sheets.

There are many great CRMs, CMSes, and other systems (I have used Drupal in the past for this niche), but they are often much more difficult to customize than Google Sheets and focused more on data storage/retrieval and less on using that data to calculate things, make graphs etc.

I know AirTable exists, it seems closer to what I want to use, but of course it is not OSS. What other "middle ground" or 'more powerful sheets' tools are out there, and are any OSS?