diff --git a/purge/README.md b/purge/README.md
index 7e0dfa1..20a8da6 100644
--- a/purge/README.md
+++ b/purge/README.md
@@ -48,6 +48,16 @@ check events of room sorted by time:
 select content, type, received_ts from events where room_id = '!scTbMproDsaihhGesQ:pixelplanet.fun' and type = 'm.room.message' order by topological_ordering limit 100;
 ```
 
+largest room by state_groups_state
+
+```sql
+SELECT s.room_id, COUNT(s.room_id)
+  FROM state_groups_state s
+  GROUP BY s.room_id 
+  ORDER BY COUNT(s.room_id) DESC
+  LIMIT 20;
+```
+
 show tables by size:
 
 ```sql