6/30

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CREATE IF NOT EXIST 문법

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CREATE IF NOT EXIST 문법

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SQL 실습

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-- 별칭주기
select ename as '이름'
from emp;

-- 중복제거
select distinct job
from emp;

-- 연결연산자
select concat(ename, 's job is', job)
from emp;

-- 연산자
select ename, sal * 12
from emp;

select ename, concat(sal*12, '만원') as '연봉'
from emp;

select ename, sal + ifnull(comm, 0)
from emp;

select * from emp
where hiredate = '1980-12-17' ;

select * from emp
where hiredate = '1980/12/17';

select * from emp
where empno = 7369;

select * from emp where sal > 2000;

select * from emp where comm is null;

select * from emp where sal = 800 and deptno = 20;

select * from emp where sal = 800 or deptno = 20;

select * from emp where hiredate between '1981-04-01' and '1987-05-02';

select * from emp where sal in (800, 1300);

select ename 
from emp
where ename like '%M%';

select ename from emp where ename like '_M%';
select ename from emp where ename like '%M';

select * from emp where job = 'CLERK' order by sal desc;

1.고정길이 출력
2.복호화 불가
3.경험에 의한 원본데이터

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SQL 실습 -CH07

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SQL 실습 CH08

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-->실제로는 having을 쓰지 않고, 다음과 같이 많이 사용한다.

select * from (
select substr(jumin, 1,2) 'birth', avg(weight) as avgsal
from student
group by substr(jumin, 1,2)
) as emp2
where emp2.avgsal >= 45;