使用遞迴查詢

SQL Server 的階層式與遞迴查詢

Jasmin Ludolf

Content Developer

IT 組織的階層

組織由下列欄位描述：

ID－員工編號
員工的 Name
在公司的 JobTitle
在公司的 Department
在公司的 Supervisor

描述階層的欄位：

ID
Supervisor

員工 2 的 Supervisor 是 1

IT 組織

+-----------------------+---------------------+------------+------------+
|ID | Name              | Position            | Department | Supervisor |    
|-----------------------|---------------------|------------|------------|
| 1 | Heinz Griesser    | IT Director         | IT         | 0          |
| 2 | Andreas Sitter    | Security Manager    | IT         | 1          |
| 3 | Thomas Bergman    | Innovation Manager  | IT         | 1          |
| 4 | Hannes Berg       | Operation Manager   | IT         | 1          |
| 5 | Anna Kruggel      | Administrator       | IT         | 4          |
| 6 | Karin Pacher      | Developer           | IT         | 4          |
+-----------------------+---------------------+------------+------------+

階層型資料的常見任務

取得單筆的階層關係

你的主管是誰？

取得階層層級

取得組織的階層層級

將遞迴結果合併成單一欄位

我有哪些主管？

取得階層關係

WITH hierarchy AS (
    SELECT ID,Supervisor
        FROM employee 
        WHERE supervisor = 0

    UNION ALL
    SELECT emp.ID, emp.Supervisor
        FROM employee emp

    JOIN hierarchy
      ON emp.Supervisor = hierarchy.ID)
SELECT *
    FROM hierarchy

取得階層關係

+---+-----------+
|ID |Supervisor |
|---|-----------|
|1  | 0         |
|2  | 1         |
|3  | 2         |
+---+-----------+

取得階層層級

WITH hierarchy AS (
    SELECT ID, Supervisor, 1 as LEVEL
        FROM employee
           WHERE Supervisor = 0

    UNION ALL
    SELECT emp.ID, emp.Supervisor, LEVEL + 1
        FROM employee emp

    JOIN hierarchy
    ON emp.Supervisor = hierarchy.ID
)
SELECT *
    FROM hierarchy

取得階層層級

+---+-----------+-------|
|ID |Supervisor | Level |
|---|-----------|-------|
|1  | 0         | 0     |
|2  | 1         | 1     |
+---+-----------+-------+

將遞迴結果合併為單一欄位

WITH hierarchy AS (
    SELECT ID, Supervisor, CAST('0' AS VARCHAR(MAX)) as PATH
        FROM employee
        WHERE Supervisor = 0

    UNION ALL
    SELECT emp.ID, emp.Supervisor, Path + '->' + CAST(emp.Supervisor AS VARCHAR(MAX))
        FROM employee emp
    INNER JOIN hierarchy
    ON emp.Supervisor = hierarchy.ID
)
SELECT *
    FROM hierarchy

將遞迴結果合併為單一欄位

+-----+--------+
| PATH         |
|--------------|
| 0 -> 1 -> 4  |
+-----+--------+

查詢 IT 組織吧

SQL Server 的階層式與遞迴查詢