1) 특정 컬럼 조회

💡 SELECT [컬럼,...]From[테이블명]

예시

select*from employees;

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가공을 해서 보여주는 방법

1. 산술 표현

select first_name, family_name, salary/10000 from employees;

2. 열 이름 변경

select first_name, family_name, salary/10000 as 급여 from employees;

3. 컬럼 순서 변경

select family_name, first_name, salary * 12 as 연봉 from employees;

4. 문자열 합치기

(o) concat

select concat(family_name , first_name) as name, salary * 12 as 연봉 from employees;

(x) 연산은 자바처럼 문자열을 합쳐주지 않는다.

(x) select family_name + first_name, salary * 12 as 연봉 from employees;