按层次顺序排序表

Question

是否可以像这样按层次顺序对查询表进行排序：

预期

+----+--------+-----------+-------+--------+-----------+-----------+---------+
| ID | Code   |  Name     | Qty   | Amount | is_parent | parent_id | remarks |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 1  | ABC    | Parent1   |  2    | 1,000  |     1     |     0     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 4  | FFLK   | Product Z |  10   | 2,500  |     0     |     1     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 5  | P6DT   | Product 5 |  7    | 1,700  |     0     |     1     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 6  | P2GL   | Product T |  5    | 1,100  |     0     |     1     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 2  | DHG    | Parent2   |  5    | 1,500  |     1     |     0     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 3  | LMSJ   | Product U |  4    | 600    |     0     |     2     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+

这是原始数据表：

+----+--------+-----------+-------+--------+-----------+-----------+---------+
| ID | Code   |  Name     | Qty   | Amount | is_parent | parent_id | remarks |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 1  | ABC    | Parent1   |  2    | 1,000  |     1     |     0     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 2  | DHG    | Parent2   |  5    | 1,500  |     1     |     0     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 3  | LMSJ   | Product U |  4    | 600    |     0     |     2     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 4  | FFLK   | Product Z |  10   | 2,500  |     0     |     1     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 5  | P6DT   | Product 5 |  7    | 1,700  |     0     |     1     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+
| 6  | P2GL   | Product T |  5    | 1,100  |     0     |     1     | xxx     |
+----+--------+-----------+-------+--------+-----------+-----------+---------+


is_parent column = 1 if data row set to parent, 0 if data row set to child 
parent_id column = 0 if data row set to parent, depend on ID of parent data

我正在使用 SQL Server 生成数据。

Answer 1

看起来实际的问题是如何按层次顺序查询数据。这可以使用recursive queries 实现，但更快的替代方法是使用SQL Server 对hierarchical data 的支持。

以分层顺序返回数据的递归查询如下所示：

WITH h AS
(
      SELECT
             ID,Code,Name,Qty,Amount,is_parent,parent_id,remarks
      FROM
            dbo.ThatTable
      WHERE 
            parent_id=0
      UNION ALL 
      SELECT
             c.ID,c.Code,c.Name,c.Qty,c.Amount,c.is_parent,c.parent_id,c.remarks
      FROM
            dbo.ThatTable c
      INNER JOIN h ON 
            c.parent_id= h.Id
)
SELECT * FROM h

如果ID 和Parent_ID 字段已编入索引，则此查询的性能可以接受，但不是很好。

向表中添加hierarchyid 字段将使查询更简单、更快。假设有一个hierarchy 字段，查询将是：

SELECT *
FROM ThatTable
ORDER BY hierarchy

在hierarchy 上添加索引将非常快地执行此查询以及查找特定节点的子节点等任何查询。服务器无需递归查询，只需查看该单个索引即可。

文章Lesson 1: Converting a Table to a Hierarchical Structure 展示了如何使用hierarchyid 创建一个新表并从父/子数据填充它。