제2절_집합_연산자(SET_OPERATOR)
2012.03.19 07:27
제2절 집합 연산자(SET OPERATOR)
집한 연산자
- 두개 이상의 연관된 테이블에서 데이터를 조회하는 방법
- 여러개의 질의의 결과를 연결하여 하나로 결합
- 튜닝관점에서 실행계획을 분리하고자 할때
![SQL_204.jpg](http://bysql.net/files/attach/images/22118/073/023/5129d6be753df9e885c15bde8f03b5e0.jpg)
![SQL_205.jpg](http://bysql.net/files/attach/images/22118/073/023/c9e2c0892a80f4c042989f0a034b70b9.jpg)
--UNION
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES
WHERE DEPARTMENT_ID=10
UNION
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES
WHERE DEPARTMENT_ID=20
ORDER BY LAST_NAME;
![이미지 17.png](http://bysql.net/files/attach/images/22118/073/023/c6dcaa5b9a20c2e70c5f58c4720c1a58.png)
--같은 컬럼에 대한 IN연산자 대체 UNION 효과
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES
WHERE DEPARTMENT_ID IN (10, 20);
![이미지 19.png](http://bysql.net/files/attach/images/22118/073/023/42d54e0bb842fae058f36d0fb309d17d.png)
UNION ALL
UNION ALL은 UNION과 다르게 집합내에서 중복이 생길수 있음(단순 결합)
--UNION ALL
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES
WHERE DEPARTMENT_ID IN (10, 20)
UNION ALL
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES
WHERE DEPARTMENT_ID IN (10, 20)
ORDER BY LAST_NAME;
![이미지 20.png](http://bysql.net/files/attach/images/22118/073/023/0a1d6acd57bb15f8eaaa4eb8da1f63cc.png)
--MINUS
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES
WHERE DEPARTMENT_ID IN (10, 20)
MINUS
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES
WHERE DEPARTMENT_ID =10
ORDER BY LAST_NAME;
![이미지 21.png](http://bysql.net/files/attach/images/22118/073/023/8f1d0d61b8e9072c7440e189f77aa90d.png)
--NOT IN를 이용한 MINUS효과
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES A
WHERE DEPARTMENT_ID IN (10, 20)
AND EMPLOYEE_ID NOT IN
(SELECT EMPLOYEE_ID
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 10);
![이미지 22.png](http://bysql.net/files/attach/images/22118/073/023/983b78774bae076ef0e1b3e51281ac39.png)
--NOT IN를 이용한 MINUS효과
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES A
WHERE DEPARTMENT_ID IN (10, 20)
INTERSECT
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES A
WHERE DEPARTMENT_ID = 10;
![이미지 24.png](http://bysql.net/files/attach/images/22118/073/023/b4717d978884c040184626d8e2e30213.png)
--IN연산자를 이용한 INTERSECT효과
SELECT DEPARTMENT_ID, EMPLOYEE_ID, FIRST_NAME, LAST_NAME
FROM EMPLOYEES A
WHERE DEPARTMENT_ID IN (10, 20)
AND EMPLOYEE_ID IN
(SELECT EMPLOYEE_ID
FROM EMPLOYEES
WHERE DEPARTMENT_ID = 10);
![이미지 25.png](http://bysql.net/files/attach/images/22118/073/023/01a4c98128d7cd3a82229187ce7c1722.png)
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