#3 SCHEMA.create を何回も呼んでたとこ修正

migration.py

@@ -42,7 +42,7 @@ def create_queries (
 
 def add_constraints_to_queries (
 ) -> None:
-    with SCHEMA.create ('queries') as table:
+    with SCHEMA.table ('queries') as table:
         table.foreign ('user_id').references ('user_id').on ('users').on_update ('cascade').on_delete ('restrict')
 
 
@@ -60,7 +60,7 @@ def create_answers (
 
 def add_constraints_to_answers (
 ) -> None:
-    with SCHEMA.create ('answers') as table:
+    with SCHEMA.table ('answers') as table:
         table.foreign ('query_id').references ('query_id').on ('queries').on_update ('cascade').on_delete ('restrict')
 
 
@@ -86,7 +86,7 @@ def create_query_answer_histories (
 
 def add_constraints_to_query_answer_histories (
 ) -> None:
-    with SCHEMA.create ('query_answer_histories') as table:
+    with SCHEMA.table ('query_answer_histories') as table:
         table.foreign ('query_id').references ('query_id').on ('queries').on_update ('cascade').on_delete ('cascade')
         table.foreign ('answer_id').references ('answer_id').on ('answers').on_update ('cascade').on_delete ('cascade')