------ postgresql扩展extension树ltree-----
树的结构图
Top
/ | \
Science Hobbies Collections
/ | \
Astronomy Amateurs_Astronomy Pictures
/ \ |
Astrophysics Cosmology Astronomy
/ | \
Galaxies Stars Astronauts
--创建扩展
CREATE EXTENSION IF NOT EXISTS ltree;
--创建表 字段名为path，类型指定为ltree。
CREATE TABLE test (path ltree);
--插入数据
INSERT INTO test VALUES ('Top');
INSERT INTO test VALUES ('Top.Science');
INSERT INTO test VALUES ('Top.Science.Astronomy');
INSERT INTO test VALUES ('Top.Science.Astronomy.Astrophysics');
INSERT INTO test VALUES ('Top.Science.Astronomy.Cosmology');
INSERT INTO test VALUES ('Top.Hobbies');
INSERT INTO test VALUES ('Top.Hobbies.Amateurs_Astronomy');
INSERT INTO test VALUES ('Top.Collections');
INSERT INTO test VALUES ('Top.Collections.Pictures');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Stars');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Galaxies');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Astronauts');
--查询数据
select * from test
---结果--
Top
Top.Science
Top.Science.Astronomy
Top.Science.Astronomy.Astrophysics
Top.Science.Astronomy.Cosmology
Top.Hobbies
Top.Hobbies.Amateurs_Astronomy
Top.Collections
Top.Collections.Pictures
Top.Collections.Pictures.Astronomy
Top.Collections.Pictures.Astronomy.Stars
Top.Collections.Pictures.Astronomy.Galaxies
Top.Collections.Pictures.Astronomy.Astronauts
---接下来演示查询方法--
--查找所有包含Astronomy的项
SELECT path FROM test WHERE path ~ '*.Astronomy.*'
path
-----------------------------------------------
Top.Science.Astronomy
Top.Science.Astronomy.Astrophysics
Top.Science.Astronomy.Cosmology
Top.Collections.Pictures.Astronomy
Top.Collections.Pictures.Astronomy.Stars
Top.Collections.Pictures.Astronomy.Galaxies
Top.Collections.Pictures.Astronomy.Astronauts
(7 rows)
--返回指定元素的后代
SELECT path FROM test WHERE path <@ 'Top.Science'
path
------------------------------------
Top.Science
Top.Science.Astronomy
Top.Science.Astronomy.Astrophysics
Top.Science.Astronomy.Cosmology
(4 rows)
--返回从第0个开始的后两个
SELECT subpath(path,0,2) FROM test
--------结果-----
Top
Top.Science
Top.Science
Top.Science
Top.Science
Top.Hobbies
Top.Hobbies
Top.Collections
Top.Collections
Top.Collections
Top.Collections
Top.Collections
Top.Collections