[Oracle] 유니온(UNION)

// 유니온, UNION

-  JOIN이 서로 관련 있는 것들을 합친 거라면, UNION은 관련이 없어도 된다.

- 조건: 스키마가 동일해야 한다.

- 중복은 제거한다. (합집합)
   ※ UNION ALL : 중복 포함

---

- UNION

SELECT ID, NAME FROM MEMBER
    UNION
SELECT WRITER_ID, TITLE FROM NOTICE;

---

select * from tblUnionA
union
select * from tblUnionB;

---

- UNION ALL

SELECT ID, NAME FROM MEMBER
    UNION ALL
SELECT WRITER_ID, TITLE FROM NOTICE;

---

select * from tblUnionA
union all
select * from tblUnionB;

---

// 연산자

- MINUS : 중심 테이블에서 다른 테이블과 공통된 부분을 뺀다.(차집합)

- INTERSECT : 공통된 부분만 남긴다.(교집합)

---

- MINUS

SELECT ID, NAME FROM MEMBER
    MINUS
SELECT WRITER_ID, TITLE FROM NOTICE;

---

select * from tblUnionA
minus
select * from tblUnionB;


select * from tblUnionB
minus
select * from tblUnionA;

---

- INTERSECT

SELECT ID, NAME FROM MEMBER
    INTERSECT
SELECT WRITER_ID, TITLE FROM NOTICE;

---

select * from tblUnionA
intersect
select * from tblUnionB;