task: #619

README.md

@@ -44,6 +44,7 @@ Have a good contributing!
     - [595. Big Countries](./leetcode/easy/595.%20Big%20Countries.sql)
     - [596. Classes With at Least 5 Students](./leetcode/easy/596.%20Classes%20With%20at%20Least%205%20Students.sql)
     - [610. Triangle Judgement](./leetcode/easy/610.%20Triangle%20Judgement.sql)
+    - [619. Biggest Single Number](./leetcode/easy/619.%20Biggest%20Single%20Number.sql)
 2. [Medium](./leetcode/medium/)
     - [176. Second Highest Salary](./leetcode/medium/176.%20Second%20Highest%20Salary.sql)
     - [184. Department Highest Salary](./leetcode/medium/184.%20Department%20Highest%20Salary.sql)

leetcode/easy/619. Biggest Single Number.sql

@@ -0,0 +1,27 @@
+/*
+Question 619. Biggest Single Number
+Link: https://leetcode.com/problems/biggest-single-number/description/
+
+Table: MyNumbers
+
++-------------+------+
+| Column Name | Type |
++-------------+------+
+| num         | int  |
++-------------+------+
+This table may contain duplicates (In other words, there is no primary key for this table in SQL).
+Each row of this table contains an integer.
+
+
+A single number is a number that appeared only once in the MyNumbers table.
+
+Find the largest single number. If there is no single number, report null.
+*/
+
+SELECT MAX(num) AS num
+FROM (
+    SELECT num 
+    FROM MyNumbers
+    GROUP BY num
+    HAVING COUNT(num) = 1
+) AS Numbers