SQL

Meaning of Keyword : Reserved words that significance in SQL : Normally write in Capitals for distinguising with Query 1. Basic Keyword table th:fir

so far all joins are additive joins2 joins will cover use a right table to determine which records to keep in the left table(오른쪽 표를 이용해서 왼쪽 표에 남겨둘 데이터

INNER JOIN vs LEFT JOIN : Number of outcome is differentUNION and UNION ALL clauses do not do the lookup step that JOINs do. They simply stack records