Index: sql/schema_creation.sql
===================================================================
--- sql/schema_creation.sql	(revision 1a9c843acf41686a27bf5c58dc77ace2cf638132)
+++ sql/schema_creation.sql	(revision bcacc91b5770933c5f080d279be105c850b2ece9)
@@ -115,4 +115,5 @@
 CREATE TABLE payment (
     id             INTEGER PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
+    user_id        INTEGER NOT NULL REFERENCES users (id),
     enrollment_id  INTEGER NOT NULL REFERENCES enrolled_semesters (id),
     amount         INTEGER NOT NULL