view

view.sql

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+USE Study
+GO
+
+CREATE VIEW EMP30
+AS (SELECT * FROM EMPLOYEE WHERE DNO = 30)
+
+SELECT * FROM EMP30 WHERE SALARY >= 300
+
+CREATE VIEW EMPAVGSAL
+AS (SELECT AVG(SALARY) AS SALAVG FROM EMPLOYEE)
+
+SELECT * FROM EMPAVGSAL
+
+-- 인라인 뷰
+-- 조인 연산으로 조건에 맞는 모든 튜플쌍이 먼저 생성됨
+SELECT DNAME, AVG(SALARY) AS AVG_SAL 
+FROM EMPLOYEE AS E, DEPARTMENT AS D 
+WHERE E.DNO = D.DNO 
+GROUP BY DNAME
+-- 원하는 튜플만 생성 후 조인하여 연상 효율성 증가
+SELECT DNAME, AVG_SAL
+FROM (
+	SELECT DNO, AVG(SALARY) AS AVG_SAL
+	FROM EMPLOYEE
+	GROUP BY DNO
+	) AS S, DEPARTMENT D
+WHERE S.DNO = D.DNO
+
+GO
+-- WITH를 사용한 인라인뷰
+WITH S (DNO, AVG_SAL)
+AS (
+	SELECT DNO, AVG(SALARY)
+	FROM EMPLOYEE
+	GROUP BY DNO
+	)
+SELECT DNAME, AVG_SAL
+FROM S, DEPARTMENT AS D
+WHERE S.DNO = D.DNO
+
+-- 뷰 정의 보기
+SP_HELPTEXT EMP30