diff --git a/anki/deck.py b/anki/deck.py
index 1d892fbcd..100eacbe1 100644
--- a/anki/deck.py
+++ b/anki/deck.py
@@ -1750,15 +1750,9 @@ facts.modelId = :id""", id=modelId))
 insert into cardTags
 (cardId, tagId, src) values
 (:cardId, :tagId, :src)""", d)
-        tags = self.s.column0("select id from tags")
-        unused = []
-        for t in tags:
-            if not self.s.scalar(
-                "select 1 from cardTags where tagId = :d limit 1",
-                d=t):
-                unused.append(t)
-        self.s.statement("""
-delete from tags where id in %s and priority = 2""" % ids2str(unused))
+        self.s.execute(
+            "delete from tags where priority = 2 and id not in "+
+            "(select distinct tagId from cardTags)")
 
     def updateTagsForModel(self, model):
         cards = self.s.all("""