如何用Oracle实现组织结构中的汇总统计-51CTO.COM

对于一般的数据模型来说，一般是有一个事实表，若干个维度表，通过事实表与维度表的连接，实现不同层次的查询汇总。

问题是对于组织结构而言，一般所有的数据都存贮于一个表中，而且，组织结构的层次也是动态的。那么，在这种情况下，如何实现员工工资的汇总呢？一个比较有趣的问题是: 如何统计员工及其所有被管理员工的总工资，举个例子，CEO的总工资就是整个公司总有员工的总工资之和，包括他自己。

Oracle 引入了一个扩展的运算符，专门用来处理此种情形，它就是connect_by_root。当以connect_by_root修饰一个列名时，Oracle将返回根节点对应的此列的值。例如，当start with 为 last_name = ‘King’时，这时返回的所有行的connect_by_root last_name的值都将为’King’。这时，对所有行的累计就是对’King’的数据的累计了。当不指定start with 子句时，Oracle将对每个节点依次进行遍历，于是，我们可以对返回的结果对last_name进行一次group by，那么我们就得到了所有last_name对应的汇总工资了。

下面是Oracle 文档中的例子。


The following example returns the last name of each employee in department 110, each manager 1.
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above that employee in the hierarchy, the number of levels between manager and employee, 1.

and the path between the two: 1.

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SELECT last_name "Employee", CONNECT_BY_ROOT last_name "Manager",
   LEVEL-1 "Pathlen", SYS_CONNECT_BY_PATH(last_name, '/') "Path"
   FROM employees
   WHERE LEVEL > 1 and department_id = 110
   CONNECT BY PRIOR employee_id = manager_id
   ORDER BY "Employee", "Manager", "Pathlen", "Path";1.
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Employee        Manager            Pathlen Path
--------------- --------------- ---------- ------------------------------
Gietz           Higgins                  1 /Higgins/Gietz
Gietz           King                     3 /King/Kochhar/Higgins/Gietz
Gietz           Kochhar                  2 /Kochhar/Higgins/Gietz
Higgins         King                     2 /King/Kochhar/Higgins
Higgins         Kochhar                  1 /Kochhar/HigginsThe following example uses a GROUP BY clause to return the total salary of each employee in department 110 and all employees below that employee in the hierarchy: 1.
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SELECT name, SUM(salary) "Total_Salary" FROM (
   SELECT CONNECT_BY_ROOT last_name as name, Salary
      FROM employees
      WHERE department_id = 110
      CONNECT BY PRIOR employee_id = manager_id)
      GROUP BY name
   ORDER BY name, "Total_Salary";
NAME                      Total_Salary
------------------------- ------------
Gietz                             8300
Higgins                          20300
King                             20300
Kochhar                          203001.
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