#3 もしかして Nullable でも行ける?

migration.py

@@ -21,6 +21,8 @@ def main (
     create_answers ()
     create_users ()
     create_query_answer_histories ()
+    add_constraints_to_queries ()
+    add_constraints_to_answers ()
     add_constraints_to_query_answer_histories ()
 
 
@@ -38,6 +40,12 @@ def create_queries (
         table.boolean ('answered').default (False).comment ('回答済')
 
 
+def add_constraints_to_queries (
+) -> None:
+    with SCHEMA.table ('queries') as table:
+        table.foreign ('user_id').references ('id').on ('users').on_update ('cascade').on_delete ('restrict')
+
+
 def create_answers (
 ) -> None:
     with SCHEMA.create ('answers') as table:
@@ -50,6 +58,12 @@ def create_answers (
         table.boolean ('answered').default (False).comment ('回答済')
 
 
+def add_constraints_to_answers (
+) -> None:
+    with SCHEMA.table ('answers') as table:
+        table.foreign ('query_id').references ('id').on ('queries').on_update ('cascade').on_delete ('restrict')
+
+
 def create_users (
 ) -> None:
     with SCHEMA.create ('users') as table: