Solvesql Solution

- update readme

Author: SubAkBa

Solvesql/README.md

@@ -9,6 +9,7 @@
 |  1  | [두 테이블 결합하기](https://solvesql.com/problems/join/)     | JOIN/UNION                                                     | [Solution](https://github.com/SubAkBa/Algorithm_Solution/blob/master/Solvesql/Solutions/%EB%91%90%ED%85%8C%EC%9D%B4%EB%B8%94%EA%B2%B0%ED%95%A9%ED%95%98%EA%B8%B0.sql) | |
 |  2  | [레스토랑 웨이터의 팁 분석](https://solvesql.com/problems/tip-analysis/) | Aggregate                                                     | [Solution](https://github.com/SubAkBa/Algorithm_Solution/blob/master/Solvesql/Solutions/%EB%A0%88%EC%8A%A4%ED%86%A0%EB%9E%91%EC%9B%A8%EC%9D%B4%ED%84%B0%EC%9D%98%ED%8C%81%EB%B6%84%EC%84%9D.sql) | |
 |  3  | [일별 블로그 방문자 수 집계](https://solvesql.com/problems/blog-counter/) | Aggregate                                                     | [Solution](https://github.com/SubAkBa/Algorithm_Solution/blob/master/Solvesql/Solutions/%EC%9D%BC%EB%B3%84%EB%B8%94%EB%A1%9C%EA%B7%B8%EB%B0%A9%EB%AC%B8%EC%9E%90%EC%88%98%EC%A7%91%EA%B3%84.sql) | |
+|  4  | [우리 플랫폼에 정착한 판매자 2](https://solvesql.com/problems/settled-sellers-2) | Aggregate                                                     | [Solution](https://github.com/SubAkBa/Algorithm_Solution/blob/master/Solvesql/Solutions/%EC%9A%B0%EB%A6%AC%ED%94%8C%EB%9E%AB%ED%8F%BC%EC%97%90%EC%A0%95%EC%B0%A9%ED%95%9C%ED%8C%90%EB%A7%A4%EC%9E%902.sql) | |
 
 
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