Oracle SQL示例数据库

Question

我正在尝试通过它提供的html" target="_blank">数据库学习Oracle SQL。我在某处发现了要完成的任务。数据库结构由Oracle提供：

CREATE TABLE EMP
(EMPNO NUMERIC(4) NOT NULL,
ENAME VARCHAR(10),
JOB VARCHAR(9),
MGR NUMERIC(4),
HIREDATE DATETIME,
SAL NUMERIC(7, 2),
COMM NUMERIC(7, 2),
DEPTNO NUMERIC(2))

INSERT INTO EMP VALUES
(7369, 'SMITH', 'CLERK', 7902, '17-DEC-1980', 800, NULL, 20)
INSERT INTO EMP VALUES
(7499, 'ALLEN', 'SALESMAN', 7698, '20-FEB-1981', 1600, 300, 30)
INSERT INTO EMP VALUES
(7521, 'WARD', 'SALESMAN', 7698, '22-FEB-1981', 1250, 500, 30)
INSERT INTO EMP VALUES
(7566, 'JONES', 'MANAGER', 7839, '2-APR-1981', 2975, NULL, 20)
INSERT INTO EMP VALUES
(7654, 'MARTIN', 'SALESMAN', 7698, '28-SEP-1981', 1250, 1400, 30)
INSERT INTO EMP VALUES
(7698, 'BLAKE', 'MANAGER', 7839, '1-MAY-1981', 2850, NULL, 30)
INSERT INTO EMP VALUES
(7782, 'CLARK', 'MANAGER', 7839, '9-JUN-1981', 2450, NULL, 10)
INSERT INTO EMP VALUES
(7788, 'SCOTT', 'ANALYST', 7566, '09-DEC-1982', 3000, NULL, 20)
INSERT INTO EMP VALUES
(7839, 'KING', 'PRESIDENT', NULL, '17-NOV-1981', 5000, NULL, 10)
INSERT INTO EMP VALUES
(7844, 'TURNER', 'SALESMAN', 7698, '8-SEP-1981', 1500, 0, 30)
INSERT INTO EMP VALUES
(7876, 'ADAMS', 'CLERK', 7788, '12-JAN-1983', 1100, NULL, 20)
INSERT INTO EMP VALUES
(7900, 'JAMES', 'CLERK', 7698, '3-DEC-1981', 950, NULL, 30)
INSERT INTO EMP VALUES
(7902, 'FORD', 'ANALYST', 7566, '3-DEC-1981', 3000, NULL, 20)
INSERT INTO EMP VALUES
(7934, 'MILLER', 'CLERK', 7782, '23-JAN-1982', 1300, NULL, 10)

CREATE TABLE DEPT
(DEPTNO NUMERIC(2),
DNAME VARCHAR(14),
LOC VARCHAR(13) )

INSERT INTO DEPT VALUES (10, 'ACCOUNTING', 'NEW YORK')
INSERT INTO DEPT VALUES (20, 'RESEARCH', 'DALLAS')
INSERT INTO DEPT VALUES (30, 'SALES', 'CHICAGO')
INSERT INTO DEPT VALUES (40, 'OPERATIONS', 'BOSTON')

CREATE TABLE BONUS
(ENAME VARCHAR(10),
JOB VARCHAR(9),
SAL NUMERIC,
COMM NUMERIC)

CREATE TABLE SALGRADE
(GRADE NUMERIC,
LOSAL NUMERIC,
HISAL NUMERIC)

INSERT INTO SALGRADE VALUES (1, 700, 1200)
INSERT INTO SALGRADE VALUES (2, 1201, 1400)
INSERT INTO SALGRADE VALUES (3, 1401, 2000)
INSERT INTO SALGRADE VALUES (4, 2001, 3000)
INSERT INTO SALGRADE VALUES (5, 3001, 9999)

现在，我想选择在本部门和薪水最高的员工。

我写了这样的东西：

select ename, salgrade.grade, dept.dname from emp, salgrade, dept
WHERE emp.sal BETWEEN salgrade.losal AND salgrade.hisal
AND emp.deptno = dept.deptno group by salgrade.grade,  dept.dname, emp.ename

但是它不能正常工作。输出为：

ENAME    GRADE   DNAME
SMITH    1   RESEARCH
BLAKE    4   SALES
FORD     4   RESEARCH
KING     5   ACCOUNTING
SCOTT    4   RESEARCH
MILLER   2   ACCOUNTING
TURNER   3   SALES
WARD     2   SALES
MARTIN   2   SALES
ADAMS    1   RESEARCH
JONES    4   RESEARCH
JAMES    1   SALES
CLARK    4   ACCOUNTING
ALLEN    3   SALES

注意行：

WARD 2 SALES
MARTIN 2 SALES

同一部门有2名员工。

你能指出我的错误吗？

Answer 1

您没有过滤查询，这就是为什么要显示所有员工的原因。

这将过滤收入低于其部门/职等最高薪资的员工：

SELECT ename, salgrade.grade, dept.dname
  FROM emp, salgrade, dept
 WHERE emp.sal BETWEEN salgrade.losal AND salgrade.hisal
   AND emp.deptno = dept.deptno
   AND emp.sal = (SELECT MAX(sal)
                    FROM emp emp_in, salgrade grade_in
                   WHERE emp_in.sal BETWEEN grade_in.losal AND grande_in.hisal
                     AND emp_in.deptno = emp.deptno
                     AND grade_in.losal = salgrade.losal)

您仍然会发现重复的内容，例如，有两个销售人员获得了2级的最高薪水（Martin和Ward均获得了1250）。这是可以接受的，还是您需要一些其他条件来仅选择其中一个。

您可以使用row_numberanalytic函数来确保按年级/部门只返回一行（请注意，如果有重复项，则Oracle将选择任意一行）：

SELECT * FROM (
  SELECT ename, salgrade.grade, dept.dname,
         row_number() OVER (PARTITION BY dept.deptno, salgrade.grade 
                            ORDER BY emp.sal DESC) rnk
    FROM emp, salgrade, dept
   WHERE emp.sal BETWEEN salgrade.losal AND salgrade.hisal
     AND emp.deptno = dept.deptno
) WHERE rnk = 1;

ENAME       GRADE DNAME          RNK
---------- ------ -------------- ---
MILLER          2 ACCOUNTING       1 
CLARK           4 ACCOUNTING       1 
KING            5 ACCOUNTING       1 
ADAMS           1 RESEARCH         1 
FORD            4 RESEARCH         1 
JAMES           1 SALES            1 
MARTIN          2 SALES            1 
ALLEN           3 SALES            1 
BLAKE           4 SALES            1