PHP unlimited classification program_PHP tutorial

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//////Infinitely classified database design and examples
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mysql> create database db_kind;
Query OK, 1 row affected

mysql> use db_kind;
Database changed
mysql> create table tb_kind(
-> id int not null auto_increment primary key,
-> pid int,
-> path varchar(200)
-> );
Query OK, 0 rows affected

mysql> insert into tb_kind values(null,"news",0,0);
Query OK, 1 row affected

mysql> insert into tb_kind values(null,"video",0,0);
Query OK, 1 row affected

mysql> insert into tb_kind values(null,"picture",0,0);
Query OK, 1 row affected

mysql> insert into tb_kind values(null,"Blog",0,0);
Query OK, 1 row affected

mysql> insert into tb_kind values(null,"Sports News",1,"0-1");
Query OK, 1 row affected

mysql> insert into tb_kind values(null,"Entertainment News",1,"0-1");
Query OK, 1 row affected

mysql> insert into tb_kind values(null,"Financial News",1,"0-1");
Query OK, 1 row affected

mysql> select * from db_kind;
ERROR 1146: Table 'db_kind.db_kind' does not exist
mysql> select * from tb
_kind;
+----+----------+-----+------+
| id | pname | pid | path |
+----+----------+-----+------+
| 1 | News | 0 | 0 |
| 2 | Video | 0 | 0 |
| 3 | Pictures | 0 | 0 |
| 4 | Blog | 0 | 0 |
| 5 | Sports News | 1 | 0-1 |
| 6 | Entertainment News | 1 | 0-1 |
| 7 | Financial News | 1 | 0-1 |
+----+----------+-----+------+
7 rows in set
mysql> insert into tb_kind values(null,"Basketball News",5,"0-1-5");
Query OK, 1 row affected

mysql> insert into tb_kind values(null,"Football News",5,"0-1-5");
Query OK, 1 row affected

mysql> select * from tb_kind;
+----+----------+-----+-------+
| id | pname | pid | path |
+----+----------+-----+-------+
| 1 | News | 0 | 0 |
| 2 | Video | 0 | 0 |
| 3 | Pictures | 0 | 0 |
| 4 | Blog | 0 | 0 |
| 5 | Sports News | 1 | 0-1 |
| 6 | Entertainment News | 1 | 0-1 |
| 7 | Financial News | 1 | 0-1 |
| 8 | Basketball News | 5 | 0-1-5 |
| 9 | Football News | 5 | 0-1-5 |
+----+----------+-----+-------+
9 rows in set

mysql> insert into tb_kind values(null,"NBA",8,"0-1-5-8");
Query OK, 1 row affected

mysql> insert into tb_kind values(null,"CBA",8,"0-1-5-8");
Query OK, 1 row affected

mysql> select * from tb_kind;
+----+----------+-----+---------+
| id | pname | pid | path |
+----+----------+-----+---------+
| 1 | News | 0 | 0 |
| 2 | Video | 0 | 0 |
| 3 | Pictures | 0 | 0 |
| 4 | Blog | 0 | 0 |
| 5 | Sports News | 1 | 0-1 |
| 6 | Entertainment News | 1 | 0-1 |
| 7 | Financial News | 1 | 0-1 |
| 8 | Basketball News | 5 | 0-1-5 |
| 9 | Football News | 5 | 0-1-5 |
| 10 | NBA | 8 | 0-1-5-8 |
| 11 | CBA | 8 | 0-1-5-8 |
+----+----------+-----+---------+
11 rows in set

mysql> select concat(path,"-",id) from tb_kind;
+---------------------+
| concat(path,"-",id) |
+---------------------+
| 0-1 |
| 0-2 |
| 0-3 |
| 0-4 |
| 0-1-5 |
| 0-1-6 |
| 0-1-7 |
| 0-1-5-8 |
| 0-1-5-9 |
| 0-1-5-8-10 |
| 0-1-5-8-11 |
+---------------------+
11 rows in set

mysql> select concat(path,"-",id) from tb_kind;
+---------------------+
| concat(path,"-",id) |
+---------------------+
| 0-1 |
| 0-2 |
| 0-3 |
| 0-4 |
| 0-1-5 |
| 0-1-6 |
| 0-1-7 |
| 0-1-5-8 |
| 0-1-5-9 |
| 0-1-5-8-10 |
| 0-1-5-8-11 |
+---------------------+
11 rows in set

mysql> select concat(path,"-",id) as abs from tb_kind order by abs.path;
ERROR 1054 : Unknown column 'abs.path' in 'order clause'
mysql> select concat(path,"-",id) as abs from tb_kind order by abs

+------------+
| abs |
+------------+
| 0-1 |
| 0-1-5 |
| 0-1-5-8 |
| 0-1-5-8-10 |
| 0-1-5-8-11 |
| 0-1-5-9 |
| 0-1-6 |
| 0-1-7 |
| 0-2 |
| 0-3 |
| 0-4 |
+------------+
11 rows in set
mysql> select concat(path,"-",id) as,id,name,path abs from tb_kind order by abs;
ERROR 1064 : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'id,name,path abs from tb_kind order by abs' at line 1
mysql> select concat(path,"-",id) as abs,
id,pname,path abs from tb_kind order by abs;
+------------+----+----------+---------+
| abs | id | pname | abs |
+------------+----+----------+---------+
| 0-1 | 1 | 新闻 | 0 |
| 0-1-5 | 5 | 体育新闻 | 0-1 |
| 0-1-5-8 | 8 | 篮球新闻 | 0-1-5 |
| 0-1-5-8-10 | 10 | NBA | 0-1-5-8 |
| 0-1-5-8-11 | 11 | CBA | 0-1-5-8 |
| 0-1-5-9 | 9 | 足球新闻 | 0-1-5 |
| 0-1-6 | 6 | 娱乐新闻 | 0-1 |
| 0-1-7 | 7 | 财经新闻 | 0-1 |
| 0-2 | 2 | 视频 | 0 |
| 0-3 | 3 | 图片 | 0 |
| 0-4 | 4 | 博客 | 0 |
+------------+----+----------+---------+
11 rows in set
mysql>

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