连表查询

########################## RBAC ################################
DROP TABLE IF EXISTS php34_privilege;
CREATE TABLE php34_privilege
(
	id smallint unsigned not null auto_increment,
	pri_name varchar(30) not null comment ‘权限名称‘,
	module_name varchar(10) not null comment ‘模块名称‘,
	controller_name varchar(10) not null comment ‘控制器名称‘,
	action_name varchar(10) not null comment ‘方法名称‘,
	parent_id smallint unsigned not null default ‘0‘ comment ‘上级权限的ID，0：代表顶级权限‘,
	primary key (id)
)engine=MyISAM default charset=utf8 comment ‘权限表‘;

DROP TABLE IF EXISTS php34_role_privilege;
CREATE TABLE php34_role_privilege
(
	pri_id smallint unsigned not null comment ‘权限的ID‘,
	role_id smallint unsigned not null comment ‘角色的id‘,
	key pri_id(pri_id),
	key role_id(role_id)
)engine=MyISAM default charset=utf8 comment ‘角色权限表‘;

DROP TABLE IF EXISTS php34_role;
CREATE TABLE php34_role
(
	id smallint unsigned not null auto_increment,
	role_name varchar(30) not null comment ‘角色名称‘,
	primary key (id)
)engine=MyISAM default charset=utf8 comment ‘角色表‘;

DROP TABLE IF EXISTS php34_admin_role;
CREATE TABLE php34_admin_role
(
	admin_id tinyint unsigned not null comment ‘管理员的id‘,
	role_id smallint unsigned not null comment ‘角色的id‘,
	key admin_id(admin_id),
	key role_id(role_id)
)engine=MyISAM default charset=utf8 comment ‘管理员角色表‘;

DROP TABLE IF EXISTS php34_admin;
CREATE TABLE php34_admin
(
	id tinyint unsigned not null auto_increment,
	username varchar(30) not null comment ‘账号‘,
	password char(32) not null comment ‘密码‘,
	is_use tinyint unsigned not null default ‘1‘ comment ‘是否启用 1：启用0：禁用‘,
	primary key (id)
)engine=MyISAM default charset=utf8 comment ‘管理员‘;
INSERT INTO php34_admin VALUES(1,‘root‘,‘bafcbdc80e0ca50e92abe420f506456b‘,1);

# 角色表 role
#id    role_name
#-------------
# 1        a
# 2        b

# 权限表 privilege
#id    pri_name
#-------------
# 1        a
# 2        b
# 3        c

# a角色拥有bc两个权限
#php34_role_privilege
#role_id   pri_id
#--------------------
#   1        2              -->  1这个角色拥有2这个权限
#   1        3              -->  1这个角色拥有3这个权限

# 有以上五张表之后写SQL取出管理员ID为3的管理员所拥有的所有的权限
# 流程：1. 先取出3这个管理员所在的角色ID
# SELECT role_id FROM  php34_admin_role WHERE admin_id=3
# 2. 再取出这些角色所拥有的权限的ID
# SELECT pri_id FROM php34_role_privilege WHERE role_id IN (1上面的结果)
# 3. 再根据权限ID取出这些权限的信息
# SELECT * FROM php34_privilege WHERE id IN(2的结果)
# 最终：
# SELECT * FROM php34_privilege WHERE id IN(
#	SELECT pri_id FROM php34_role_privilege WHERE role_id IN (
#		SELECT role_id FROM  php34_admin_role WHERE admin_id=3
#	)
# )
# 写法二、
# SELECT a.*
#   FROM php34_privilege a,php34_role_privilege b,php34_admin_role c
#    WHERE c.admin_id=3 AND b.pri_id=a.id AND b.role_id=c.role_id
# 写法三、
# SELECT b.*
#  FROM php34_role_privilege a
#   LEFT JOIN php34_privilege b ON a.pri_id=b.id
#   LEFT JOIN php34_admin_role c ON a.role_id=c.id
#    WHERE c.admin_id=3