add 1623

fishercoder1534 · fishercoder1534 · commit e1100dc3634e · 2021-01-01T08:53:58.000-08:00
diff --git a/README.md b/README.md
@@ -1080,6 +1080,7 @@ _If you like this project, please leave me a star._ &#9733;
 |1667|[Fix Names in a Table](https://leetcode.com/problems/fix-names-in-a-table/)|[Solution](../master/database/_1667.sql) || Easy |
 |1661|[Average Time of Process per Machine](https://leetcode.com/problems/average-time-of-process-per-machine/)|[Solution](../master/database/_1661.sql) || Easy |
 |1633|[Percentage of Users Attended a Contest](https://leetcode.com/problems/percentage-of-users-attended-a-contest/)|[Solution](../master/database/_1633.sql) || Easy |
+|1623|[All Valid Triplets That Can Represent a Country](https://leetcode.com/problems/all-valid-triplets-that-can-represent-a-country/)|[Solution](../master/database/_1623.sql) || Easy |
 |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 |
diff --git a/database/_1623.sql b/database/_1623.sql
@@ -0,0 +1,10 @@
+--# Write your MySQL query statement below
+select a.student_name as member_A,
+b.student_name as member_B,
+c.student_name as member_C
+from SchoolA a cross join SchoolB b cross join SchoolC c where a.student_name != b.student_name and
+a.student_id != b.student_id and
+b.student_name != c.student_name and
+b.student_id != c.student_id and
+a.student_name != c.student_name and
+a.student_id != c.student_id;
