refactor 1322

Author: fishercoder1534

Diff for: database/_1322.sql

@@ -1,62 +1,3 @@
---1322. Ads Performance
---
---Table: Ads
---
---+---------------+---------+
---| Column Name   | Type    |
---+---------------+---------+
---| ad_id         | int     |
---| user_id       | int     |
---| action        | enum    |
---+---------------+---------+
---(ad_id, user_id) is the primary key for this table.
---Each row of this table contains the ID of an Ad, the ID of a user and the action taken by this user regarding this Ad.
---The action column is an ENUM type of ('Clicked', 'Viewed', 'Ignored').
---
---
---A company is running Ads and wants to calculate the performance of each Ad.
---
---Performance of the Ad is measured using Click-Through Rate (CTR) where:
---
---
---
---Write an SQL query to find the ctr of each Ad.
---
---Round ctr to 2 decimal points. Order the result table by ctr in descending order and by ad_id in ascending order in case of a tie.
---
---The query result format is in the following example:
---
---Ads table:
---+-------+---------+---------+
---| ad_id | user_id | action  |
---+-------+---------+---------+
---| 1     | 1       | Clicked |
---| 2     | 2       | Clicked |
---| 3     | 3       | Viewed  |
---| 5     | 5       | Ignored |
---| 1     | 7       | Ignored |
---| 2     | 7       | Viewed  |
---| 3     | 5       | Clicked |
---| 1     | 4       | Viewed  |
---| 2     | 11      | Viewed  |
---| 1     | 2       | Clicked |
---+-------+---------+---------+
---Result table:
---+-------+-------+
---| ad_id | ctr   |
---+-------+-------+
---| 1     | 66.67 |
---| 3     | 50.00 |
---| 2     | 33.33 |
---| 5     | 0.00  |
---+-------+-------+
---for ad_id = 1, ctr = (2/(2+1)) * 100 = 66.67
---for ad_id = 2, ctr = (1/(1+2)) * 100 = 33.33
---for ad_id = 3, ctr = (1/(1+1)) * 100 = 50.00
---for ad_id = 5, ctr = 0.00, Note that ad_id = 5 has no clicks or views.
---Note that we don't care about Ignored Ads.
---Result table is ordered by the ctr. in case of a tie we order them by ad_id
-
 --# Write your MySQL query statement below
 select ad_id,
 ifnull(