SMS and MMS messages are stored in the same database. In our experience, this database is also used, regardless of what application is used to send the SMS/MMS (that is, sending an SMS through Google Hangouts will populate this database, not the Hangouts database examined here). However, third-party apps may also record the data in their own databases.
Version: Default version with Android 5.0.1 (not listed within app)
Files of interest:
app_parts directory contains attachments sent as an MMS, both sent and received.
This contains historical data for all SIMs that have been used in the device, including the ICCID, phone number (if it was stored on the SIM), and the mobile country code (MCC) / mobile network...