多表连接查询

找出每个员工的部门名称和工资等级

SELECT
    E.ENAME, D.DNAME, S.GRADE
FROM
    EMP E
JOIN
    DEPT D
ON
    E.DEPTNO = D.DEPTNO
JOIN
    SALGRADE S
ON
    E.SAL BETWEEN S.LOSAL AND S.HISAL;

找出每个员工的部门名称、工资等级和上级领导

SELECT
    E.ENAME AS '员工', D.DNAME, S.GRADE, E1.ENAME AS '领导'
FROM
    EMP E
JOIN
    DEPT D
ON
    E.DEPTNO = D.DEPTNO
JOIN
    SALGRADE S
ON
    E.SAL BETWEEN S.LOSAL AND S.HISAL
LEFT JOIN
    EMP E1
ON
    E.MGR = E1.EMPNO;