Create ads-performance.sql

Author: kamyu104

MySQL/ads-performance.sql

@@ -0,0 +1,23 @@
+# Time:  O(nlogn)
+# Space: O(n)
+
+SELECT ad_id,
+       CASE
+           WHEN clicks + views = 0 THEN 0
+           ELSE ROUND(100 * clicks / (clicks + views), 2)
+       END ctr
+FROM
+  (SELECT ad_id,
+          SUM(CASE
+                  WHEN action ='Viewed' THEN 1
+                  ELSE 0
+              END) views,
+          SUM(CASE
+                  WHEN action = 'Clicked' THEN 1
+                  ELSE 0
+              END) clicks
+   FROM Ads
+   GROUP BY ad_id) a
+ORDER BY ctr DESC,
+         ad_id ASC
+