목록2024/11/08 (1)

개발노트

EQUI JOIN

JOIN일반적으로 PK, FK를 이용논리적 관계만으로 가능테이블 여러개 조인해도 2개씩 조인JOIN A, B, C,D -> JOIN(JOIN(JOIN(A,B), C), D)EQUI JOIN테이블 간의 칼럼 값들이 정확히 일치 할때JOIN 대상 테이블이 N개라면 EQUI JOIN은 조인 조건 N-1개 필요SELECT EMP.EMPNO, EMP.ENAME, DEPT.DNAMEFROM EMP, DEPTWHERE EMP.DEPTNO = DEPT.DEPTNO; [제약사항]ALIAS를 사용하면 기존 테이블의 이름 사용 불가능ALIAS를 사용하면 ALIAS만 사용가능FROM에 AS 사용 불가 조건 추가해서 사용 가능SELECT A.EMPNO, A.ENAME, B.DNAMEFROM EM..
자격증/SQLD 2024. 11. 8. 14:07
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