Index: sql/schema_creation.sql
===================================================================
--- sql/schema_creation.sql	(revision e7bafc08ad74099b6daf91b8414b90e3c4968111)
+++ sql/schema_creation.sql	(revision 002cf5f9fe36565e030e882d63222c760d638995)
@@ -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