문제 : https://leetcode.com/problems/combine-two-tables/description/ 풀이:# 방법1. LEFT JOIN (가장 일반적인 방법)SELECT p.firstName, p.lastName, a.city, a.stateFROM person pLEFT JOIN address aON p.personId = a.personId;# 방법2. COALESCE (lEFT JOIN 과 효율성 동일 단지 결과 가공용)SELECT p.firstName, p.lastName, COALESCE(a.city, NULL ) AS city, COALESCE(a.state, NULL ) AS stateFROM Person pLEFT JOIN ..