Based on our record, H2 Database Engine seems to be more popular. It has been mentiond 2 times since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Not sure of your use case, maybe you could use an embedded database (ie h2). Source: over 3 years ago
There are in-memory databases such as H2 which you can use for testing that is just a library you import. However, syntax can vary between databases. So it's only really appropriate if you're also using something like Hibernate which abstracts away a lot of the differences. Source: over 3 years ago
Redis - Redis is an open source in-memory data structure project implementing a distributed, in-memory key-value database with optional durability.
4D - 4D is a relational database management system and IDE.
MongoDB - MongoDB (from "humongous") is a scalable, high-performance NoSQL database.
LiveCode Platform - It is Both Under the GPL and it is also Proprietary if using the GPL version the software you make...
SQLite - SQLite Home Page
Informix - IBM Informix is a secure embeddable database optimized for OLTP and IoT data. Informix can seamlessly integrate SQL, NoSQL/JSON, and time series and spatial data.