diff --git a/amaksatov/postgresql/OS-330.sql b/amaksatov/postgresql/OS-330.sql
index 86a034c..beeae0e 100644
--- a/amaksatov/postgresql/OS-330.sql
+++ b/amaksatov/postgresql/OS-330.sql
@@ -6,14 +6,10 @@ SELECT
     COUNT(DISTINCT lv.lesson_id) AS viewed_lessons_count,
     MAX(lv.viewed_at) AS last_viewed,
     MIN(lv.viewed_at) AS first_viewed,
-    ROUND (
-        CASE
-            WHEN COUNT(DISTINCT l.id) = 0 THEN NULL
-            ELSE COUNT(DISTINCT lv.lesson_id) * 1.0 / COUNT(DISTINCT l.id) * 100
-        END, 2)::TEXT || '%' AS "engagement_rate"
+    ROUND (COUNT(DISTINCT lv.lesson_id) * 1.0 / NULLIF(COUNT(DISTINCT l.id), 0) * 100, 2) AS "engagement_rate(%)"
 FROM amaksatov.users u
 LEFT JOIN enrollments e ON e.user_id = u.id
 LEFT JOIN lessons l ON l.course_id = e.course_id
 LEFT JOIN lesson_views lv ON lv.lesson_id = l.id AND u.id = lv.user_id
-GROUP BY u.id
-HAVING COUNT(e.id) > 0;
\ No newline at end of file
+GROUP BY u.id;
+