Some registered users have null values for one of the user name fields. This seems to fit one of two patterns:
- A revision event has a null event_user_text, even though event_user_text_historical and event_user_id match and are correct and there is no indication the user has ever been renamed.
- A page or user event has event_user_text, event_user_text_historical, and event_user_is_anonymous as null, even though event_user_id is correct
- S7w4j9 (user ID 64) on yuewiktionary
- Rovack (user ID 467551) on enwiki
- SheriffsIsInTown (user ID 2987925) on dewiki
For a query showing the number of affected rows, see P8210.