MySQL模拟Oracle邻接模型树形处理 - 数据库编程

数据库对层次结构的处理模型有好多种，可以根据自己的需求来设计模型，当然最简单的也是最容易设计的模型就是所谓的邻接模型。在这方面，其他数据库比如Oracle 提供了现成的分析方法 connect by，而MySQL在这方面就显得有些薄弱了。不过可以用MySQL的存储过程实现ORACLE类似的分析功能
create table country ( id number(2) not null, name varchar(60) not null); create table country_relation (id number(2), parentid number(2));
-- Table country. insert into country (id,name) values (0,'Earth'); insert into country (id,name) values (2,'North America'); insert into country (id,name) values (3,'South America'); insert into country (id,name) values (4,'Europe'); insert into country (id,name) values (5,'Asia'); insert into country (id,name) values (6,'Africa'); insert into country (id,name) values (7,'Australia'); insert into country (id,name) values (8,'Canada'); insert into country (id,name) values (9,'Central America'); insert into country (id,name) values (10,'Island Nations'); insert into country (id,name) values (11,'United States'); insert into country (id,name) values (12,'Alabama'); insert into country (id,name) values (13,'Alaska'); insert into country (id,name) values (14,'Arizona'); insert into country (id,name) values (15,'Arkansas'); insert into country (id,name) values (16,'California'); -- Table country_relation. insert into country_relation (id,parentid) values (0,NULL); insert into country_relation (id,parentid) values (2,0); insert into country_relation (id,parentid) values (3,0); insert into country_relation (id,parentid) values (4,0); insert into country_relation (id,parentid) values (5,0); insert into country_relation (id,parentid) values (6,0); insert into country_relation (id,parentid) values (7,0); insert into country_relation (id,parentid) values (8,2); insert into country_relation (id,parentid) values (9,2); insert into country_relation (id,parentid) values (10,2); insert into country_relation (id,parentid) values (11,2); insert into country_relation (id,parentid) values (12,11); insert into country_relation (id,parentid) values (13,11); insert into country_relation (id,parentid) values (14,11); insert into country_relation (id,parentid) values (15,11); insert into country_relation (id,parentid) values (16,11);
select max(level) "level" from COUNTRY_RELATION a start with a.parentid is NULL connect by PRIOR a.id = a.PARENTID order by level; level ---------- 4 已用时间: 00: 00: 00.03

select name from ( select b.name, connect_by_isleaf "isleaf" from COUNTRY_RELATION a inner join country b on (a.id = b.id) start with a.parentid is NULL connect by prior a.id = a.PARENTID ) T where T."isleaf" = 1; NAME -------------------------------------------------- Canada Central America Island Nations Alabama Alaska Arizona Arkansas California South America Europe Asia Africa Australia 已选择13行。已用时间: 00: 00: 00.01
select connect_by_root b.name from COUNTRY_RELATION a inner join country b on (a.id = b.id) start with a.parentid is NULL connect by a.id = a.PARENTID CONNECT_BY_ROOTB.NAME -------------------------------------------------- Earth 已用时间: 00: 00: 00.01
select sys_connect_by_path(b.name,'/') "path" from COUNTRY_RELATION a inner join country b on (a.id = b.id) start with a.parentid is NULL connect by prior a.id = a.PARENTID order by level,a.id; path -------------------------------------------------- /Earth /Earth/North America /Earth/South America /Earth/Europe /Earth/Asia /Earth/Africa /Earth/Australia /Earth/North America/Canada /Earth/North America/

MySQL模拟Oracle邻接模型树形处理(一)