Axxon PSIM is able to work with following versions:
SQL Server 2014
SQL Server 2016
SQL Server 2017
SQL Server 2019
Axxon PSIM installer includes SQL Server 2014 Express. It will be installed automatically if no any SQL Server installed on PC.
Warning: SQL Server Express edition has limit 10 Gb of database size. If you expect a lot of events stored in a database you should use SQL Server Standart edition.