From your reply it is implied that one can parse and create a database of specific tags from EXIT, IPTC & XMP but cannot parse MakerNotes (since they are not standard). In other words any searches on MakerNotes is not possible from the database except for those tags in MakerNotes that are also available in EXIF!
Does lightroom for example, store makernotes tags in SQLite database?
Possibly; information (derived from) the makernotes might be essential for processing raw data and they may have chosen to keep this in their database for quick retrieval.
But I think you misunderstood what I wanted to say. It is definitely possible to store makernote fields in a database. Just not all will be there and not all fields will mean the exact same thing for each camera (brand). So when you retrieve data from your database you will need to apply some logic as to how the data should be interpreted based on brand and model.
Also important to note is that the same tag sometimes is present in multiple locations in a file (each may even have a different value!). So perhaps you want to store the "group" the data comes from as well (use -G0:1
to get precise location info). To get the tags from all locations, use -a