@markleo said in For large Qt desktop projects, how is the database generally used in combination?:
Since large databases such as MySQL and PostgreSQL need to be installed on a PC
Those are typically installed on a server and clients access that server. It would be unusual to install such SQL servers on users machines.
Whether SQLite is sufficient or not really depends on your needs. It is, for example, not designed to be accessed in parallel by several applications at the same time. So, what are your requirements? Are your clients going to access same databases? If so, you should consider client/server architecture using MySQL/PostgreSQL.