Relational databases are typically resource-intensive and not commonly run on microcontrollers, which usually have limited processing power and storage capacity. However, there are some lightweight databases that can run on microcontrollers with constrained resources.

LittleD is a relational database for microprocessor devices, using as little as 1kB of RAM for most queries. This currently has 713 stars on GitHub. The GitHub address is: https://github.com/graemedouglas/LittleD

As setup steps can change frequently, it’s best to refer to the latest documentation in their repository. First view the Readme.md. Currently the latest docs specify to use the make command to build the library and utilities. Look in the LittleD/arduino/sketch.ino for example usage.
spam fails_task lang_mismatch pii not_appropriate hate_speech sexual_content quality toxicity humor helpfulness creativity violence