Oracle如何实现层次化查询

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Oracle层次化查询

(1) 树状模型

假如有一个市场模型，其中一级市场是中国，二级市场是省份，三级市场是各个省下面的市，四级市场是各个市下面的县。那么可以创建表market：

create
table market(market_id number(2), market_name varchar2(10),
parent_market_id number(2));

insert
all

into
market values(1, 'China', 0)

into
market values(2, 'Shan Xi', 1)

into
market values(3, 'Shan Dong', 1)

into
market values(4, 'Fu Jian', 1)

into
market values(5, 'Tai Yuan', 2)

into
market values(6, 'Yang Quan', 2)

into
market values(7, 'Qi Zhou', 2)

into
market values(8, 'Qing Dao', 3)

into
market values(9, 'Ji Nan', 3)

into
market values(10, 'Yan Tai', 3)

into
market values(11, 'Xia Men', 4)

into
market values(12, 'Fu Zhou', 4)

into
market values(13, 'Quan Zhou', 4)

into
market values(14, 'Gu Jiao', 5)

into
market values(15, 'Yang Qu', 5)

into
market values(16, 'Qing Xu', 5)

select
* from dual;

(2) 层次化查询

select
market_id, market_name

from
market

start
with market_name = 'Shan Xi'

connect
by prior market_id = parent_market_id;

MARKET_ID
MARKET_NAME

———-
——————————

2 Shan Xi

5 Tai Yuan

14
Gu Jiao

15
Yang Qu

16
Qing Xu

6 Yang Quan

7 Qi Zhou

7
rows selected.

这里的搜索规则为：从'Shan
Xi'节点开始搜索、前一个节点的market_id等于下一个节点的parent_markket_id。

(3) 相关函数

显示搜索路径的函数为

sys_connect_by_path（列名，分隔符）

示例：

select
market_id, market_name, sys_connect_by_path(market_name, '/') as
market_path

from
market

start
with market_name = 'Gu Jiao'

connect
by prior parent_market_id = market_id;

MARKET_ID
MARKET_NAM MARKET_PATH

———-
———- —————————————-

14
Gu Jiao    /Gu Jiao

5 Tai Yuan   /Gu Jiao/Tai Yuan

2 Shan Xi    /Gu Jiao/Tai Yuan/Shan Xi

1 China      /Gu Jiao/Tai Yuan/Shan Xi/China

这里可以利用max()函数来获得完整的路径：

select
max(sys_connect_by_path(market_name, '/')) market_path

from
market

start
with market_name = 'Gu Jiao'

connect
by prior parent_market_id = market_id;

MARKET_PATH

—————————————-

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