add 580

fishercoder1534 · fishercoder1534 · commit 05f03512eec9 · 2017-07-22T17:12:44.000-07:00
diff --git a/README.md b/README.md
@@ -575,6 +575,7 @@ Your ideas/fixes/algorithms are more than welcome!
 |595|[Big Countries](https://leetcode.com/problems/big-countries/)|[Solution](../master/database/_595.sql) | O(n) |O(1) | Easy |
 |586|[Customer Placing the Largest Number of Orders](https://leetcode.com/problems/customer-placing-the-largest-number-of-orders/)|[Solution](../master/database/_586.sql) | | | Easy|
 |584|[Find Customer Referee](https://leetcode.com/problems/find-customer-referee/)|[Solution](../master/database/_584.java) | || Easy|
+|580|[Count Student Number in Departments](https://leetcode.com/problems/count-student-number-in-departments/)|[Solution](../master/database/_580.sql) | || Medium | Left Join
 |577|[Employee Bonus](https://leetcode.com/problems/employee-bonus/)|[Solution](../master/database/_577.sql) | || Easy |
 |197|[Rising Temperature](https://leetcode.com/problems/rising-temperature/)|[Solution](../master/database/RisingTemperature.sql)| O(n^2)|O(n) | Easy|
 |196|[Delete Duplicate Emails](https://leetcode.com/problems/delete-duplicate-emails/)|[Solution](../master/database/DeleteDuplicateEmails.sql)| O(n^2)|O(n) | Easy|
diff --git a/database/_580.sql b/database/_580.sql
@@ -0,0 +1,4 @@
+select d.dept_name, count(s.student_id) as student_number
+    from department d left join student s on d.dept_id = s.dept_id
+    group by d.dept_name
+    order by student_number desc, d.dept_name;
