diff --git a/database/schema.ts b/database/schema.ts
index bff5ea5..37f009b 100644
--- a/database/schema.ts
+++ b/database/schema.ts
@@ -580,7 +580,12 @@ export const eventResults = pgTable("event_results", {
   rawScore: decimal("raw_score", { precision: 10, scale: 2 }), // strokes, points, time, etc.
   createdAt: timestamp("created_at").defaultNow().notNull(),
   updatedAt: timestamp("updated_at").defaultNow().notNull(),
-});
+}, (t) => ({
+  uniqueEventParticipant: uniqueIndex("event_results_event_participant_unique").on(
+    t.scoringEventId,
+    t.seasonParticipantId,
+  ),
+}));
 
 // Playoff bracket matches (for display and tracking)
 export const playoffMatches = pgTable("playoff_matches", {