Leetcode SQL: confirmation rate
Leetcode SQL: Confirmation Rate Solution
This SQL script calculates the confirmation rate for user signups. Let's break it down step-by-step:
WITH t AS (...): This part creates a temporary table named t that holds specific data for later use.
SELECT s.user_id, ... FROM Signups s LEFT JOIN Confirmations c ON s.user_id = c.user_id:
This line selects the user_id from the Signups table (s).
It performs a left join with the Confirmations table (c) where the user_id from Signups matches the user_id in Confirmations. This means it includes all users from Signups and their corresponding confirmations if they exist.
COUNT(... CASE WHEN c.action = 'confirmed' THEN 1 ELSE NULL END) AS confirmations:
This counts the number of times the action is 'confirmed' for each user.
It uses a case statement to count 1 if the action is 'confirmed' and null otherwise.
COUNT(1) AS requests:
This counts the total number of signups (requests) for each user.
GROUP BY 1:
This groups the results by the first column, which is s.user_id.
SELECT user_id, ROUND(confirmations / (requests * 1.0), 2) AS confirmation_rate FROM t:
This selects the user_id and calculates the confirmation rate by dividing the number of confirmations by the total requests.
The ROUND function is used to round the confirmation rate to two decimal places.
Summary
This SQL query calculates the confirmation rate of user signups by:
Creating a temporary table with the number of confirmations and total signups for each user.
Joining the Signups and Confirmations tables to gather data.
Counting confirmations and requests for each user.
Calculating and rounding the confirmation rate for each user.
By understanding this query, you can see how SQL is used to analyze user behavior and calculate important metrics, which is a valuable skill in data analysis and database management.
Leet Code Instructions:
Table: Signups
+----------------+----------+
| Column Name | Type |
+----------------+----------+
| user_id | int |
| time_stamp | datetime |
+----------------+----------+
user_id is the column of unique values for this table.
Each row contains information about the signup time for the user with ID user_id.
Table: Confirmations
+----------------+----------+
| Column Name | Type |
+----------------+----------+
| user_id | int |
| time_stamp | datetime |
| action | ENUM |
+----------------+----------+
(user_id, time_stamp) is the primary key (combination of columns with unique values) for this table.
user_id is a foreign key (reference column) to the Signups table.
action is an ENUM (category) of the type ('confirmed', 'timeout')
Each row of this table indicates that the user with ID user_id requested a confirmation message at time_stamp and that confirmation message was either confirmed ('confirmed') or expired without confirming ('timeout').
The confirmation rate of a user is the number of 'confirmed' messages divided by the total number of requested confirmation messages. The confirmation rate of a user that did not request any confirmation messages is 0. Round the confirmation rate to two decimal places.
Write a solution to find the confirmation rate of each user.
Return the result table in any order.
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