Looking for non-SQL, more advanced than key-value store databases, let me expand the list to the top 20, and annotate the FOSS databases that fall between those two types, are not solely cloud hosted ($$ and also probably not FOSS), and are in the top 20 of each list:

From: Amirouche Boubekki <xxxxxx@gmail.com>
Date: Friday, September 13, 2019 7:37 PM

About the topic of this thread

According to  https://db-engines.com/en/ranking the top 10 databases is:

  • Oracle
  • MySQL
  • MS SQL Server
  • PostgreSQL
  • MongoDB
  • IBM Db2
  • Elatissearch - full text search plus JSON Document
  • Redis 
  • MS Access (!)
  • Cassandra - Wide Column

Here's a definition of wide column databases: https://db-engines.com/en/article/Wide+Column+Stores

Wide column stores, also called extensible record stores, store data in records with an ability to hold very large numbers of dynamic columns. Since the column names as well as the record keys are not fixed, and since a record can have billions of columns, wide column stores can be seen as two-dimensional key-value stores.

Wide column stores share the characteristic of being schema-free with document stores, however the implementation is very different.

According to StackOverflow survey 2018:

  • MySQL
  • MS SQL Server
  • PostgreSQL
  • MongoDB
  • SQLite
  • Redis
  • ElasticSearch - full text search plus JSON Document
  • MariaDB (MySQL fork)
  • Oracle
  • MS Azure (Tables, CosmosDB, SQL, etc)

https://insights.stackoverflow.com/survey/2018/#technology-_-databases

Based on this it very clear SQL support is the big name.

There is ElasticSearch, MongoDB and REDIS.

My knowledge of ElasticSearch is not good enough to tell whether
it can share a similar interface to SQL DBs, I would say it depends
of the interface. I would say "maybe yes" if we exclude the query
language from the specification.

Similarly, MongoDB works using the same principles as SQL when
you consider that it it takes a query as input and outputs a list of objects.
Unlike SQL objects are free-form.

[ REDIS is a mistake. ]

I'd add that MongoDB, "the Snapchat of databases", is now so full of fail due to the change to a non-FOSS license, and for example thus getting dropped by many distributions, that it should also be avoided.

So we could add to consideration the Wide Column Cassandra and Apache HBase, and the Graph Neo4j databases.

Any thoughts on adding to the lowest "plumbing" level a Wide Column, and maybe a Graph database, along with ElasticSearch?

- Harold