add 1581

Author: fishercoder1534

README.md

@@ -1057,6 +1057,7 @@ _If you like this project, please leave me a star._ ★
 |  #  |      Title     |   Solutions   | Video         | Difficulty    | Tag          
 |-----|----------------|---------------|---------------|---------------|-------------
 |1607|[Sellers With No Sales](https://leetcode.com/problems/sellers-with-no-sales/)|[Solution](../master/database/_1607.sql) || Easy |
+|1581|[Customer Who Visited but Did Not Make Any Transactions](https://leetcode.com/problems/customer-who-visited-but-did-not-make-any-transactions/)|[Solution](../master/database/_1581.sql) || Easy |
 |1543|[Fix Product Name Format](https://leetcode.com/problems/fix-product-name-format/)|[Solution](../master/database/_1543.sql) || Easy |
 |1517|[Find Users With Valid E-Mails](https://leetcode.com/problems/find-users-with-valid-e-mails/)|[Solution](../master/database/_1517.sql) || Easy |
 |1495|[Friendly Movies Streamed Last Month](https://leetcode.com/problems/friendly-movies-streamed-last-month/)|[Solution](../master/database/_1495.sql) || Easy |

database/_1581.sql

@@ -0,0 +1,2 @@
+--# Write your MySQL query statement below
+select customer_id as customer_id, count(*) as count_no_trans from Visits where visit_id not in (select distinct visit_id from Transactions) group by customer_id;