task: #1581

Author: Ivanbyone

README.md

@@ -57,6 +57,7 @@ Have a good contributing!
     - [1378. Replace Employee ID With The Unique Identifier](./leetcode/easy/1378.%20Replace%20Employee%20ID%20With%20The%20Unique%20Identifier.sql)
     - [1407. Top Travellers](./leetcode/easy/1407.%20Top%20Travellers.sql)
     - [1484. Group Sold Products By The Date](./leetcode/easy/1484.%20Group%20Sold%20Products%20By%20The%20Date.sql)
+    - [1581. Customer Who Visited but Did Not Make Any Transactions](./leetcode/easy/1581.%20Customer%20Who%20Visited%20but%20Did%20Not%20Make%20Any%20Transactions.sql)
     - [1587. Bank Account Summary II](./leetcode/easy/1587.%20Bank%20Account%20Summary%20II.sql)
     - [1633. Percentage of Users Attended a Contest](./leetcode/easy/1633.%20Percentage%20of%20Users%20Attended%20a%20Contest.sql)
     - [1683. Invalid Tweets](./leetcode/easy/1683.%20Invalid%20Tweets.sql)

leetcode/easy/1581. Customer Who Visited but Did Not Make Any Transactions.sql

@@ -0,0 +1,56 @@
+/*
+Question 1581. Customer Who Visited but Did Not Make Any Transactions
+Link: https://leetcode.com/problems/customer-who-visited-but-did-not-make-any-transactions/description/?envType=study-plan-v2&envId=top-sql-50
+
+Table: Visits
+
++-------------+---------+
+| Column Name | Type    |
++-------------+---------+
+| visit_id    | int     |
+| customer_id | int     |
++-------------+---------+
+visit_id is the column with unique values for this table.
+This table contains information about the customers who visited the mall.
+ 
+
+Table: Transactions
+
++----------------+---------+
+| Column Name    | Type    |
++----------------+---------+
+| transaction_id | int     |
+| visit_id       | int     |
+| amount         | int     |
++----------------+---------+
+transaction_id is column with unique values for this table.
+This table contains information about the transactions made during the visit_id.
+ 
+
+Write a solution to find the IDs of the users who visited without making any transactions and the number of times they made these types of visits.
+
+Return the result table sorted in any order.
+*/
+
+SELECT 
+    customer_id,
+    COUNT(visit_id) AS count_no_trans
+FROM Visits
+WHERE
+    visit_id NOT IN (
+        SELECT DISTINCT t.visit_id
+        FROM Transactions AS t
+    )
+GROUP BY customer_id;
+
+-- OR
+
+SELECT 
+    v.customer_id,
+    COUNT(v.visit_id) AS count_no_trans
+FROM Visits AS v
+LEFT JOIN
+    Transactions AS t
+    ON v.visit_id = t.visit_id
+WHERE t.visit_id IS NULL
+GROUP BY v.customer_id