数据库字段 visible set('user','memb','agent','adm') NOT NULL default 'user',
条件 WHERE visible & 3 是什么意思
SELECT * FROM AgentsDesc WHERE visible & 3
帮我问下。
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下面是表，供测试，我怎么测试都不对，晕，
CREATE TABLE AgentsDesc (ID int(10) unsigned NOT NULL auto_increment,name varchar(64) NOT NULL default '',namedisp varchar(255) NOT NULL default '',namenote varchar(255) NOT NULL default '',extra mediumtext NOT NULL,type enum('d','f','c','p','e','en','a','s','0','r','rb','set','eny','rr','js') NOT NULL default 'd',order float NOT NULL default '0',join_page float NOT NULL default '0',profile_type varchar(10) NOT NULL default 'single',visible set('user','memb','agent','adm') NOT NULL default 'user',editable set('memb','agent','adm') NOT NULL default 'agent,adm',check varchar(255) NOT NULL default '',because varchar(255) NOT NULL default '',group_mark enum('','b','c','e') NOT NULL default '',group_text_b varchar(32) NOT NULL default '',group_text_a varchar(32) NOT NULL default '',to_db int(11) NOT NULL default '1',show_on_page set('0','3','7','25') NOT NULL default '0',get_value varchar(255) NOT NULL default '',get_value_db varchar(255) NOT NULL default '',search_type enum('none','radio','list','check','daterange','check_set','text','js') default 'none',search_cols int(11) NOT NULL default '0',search_hide tinyint(4) NOT NULL default '0',search_extra varchar(255) NOT NULL default '',search_order float NOT NULL default '0',search_default varchar(255) NOT NULL default '',search_where varchar(255) NOT NULL default '',match_field varchar(64) NOT NULL default '',match_type enum('none','enum','enum_ref','set','daterange') NOT NULL default 'none',match_extra varchar(255) NOT NULL default '',min_length varchar(5) NOT NULL default '',max_length varchar(5) NOT NULL default '',
PRIMARY KEY (ID),
UNIQUE KEY name (name)
) type=MyISAM AUTO_INCREMENT=151 ;
--
-- 导出表中的数据 AgentsDesc
--
INSERT INTO AgentsDesc VALUES (3, 'Name', '_Name_caption', '_AGENT_LEAST', '40', 'c', 1, 1020, 'single', 'user,agent,adm', 'agent,adm', 'return (strlen($arg0) >= 2 && strlen($arg0) <= 20 ) ? true : false;', '_AGENT_LEAST', '', '', '', 1, '3,25', '', '', 'none', 0, 0, '', 0, '', '', '', 'none', '', '2', '20');
INSERT INTO AgentsDesc VALUES (4, 'Contact', '_Contact_caption', '_Use latin set', '40', 'c', 4, 1030, 'single', 'memb,adm', 'memb,adm', 'return strlen($arg0) > 0 ? true : false;', '_Contact_err_msg', '', '', '', 1, '0', '', '', 'none', 0, 0, '', 0, '', '', '', 'none', '', '', '');
INSERT INTO AgentsDesc VALUES (6, 'Country', '_Country', '_MUST_BE_VALID', '', 'js', 5.5, 2020, 'single', 'user,agent,adm', 'agent,adm', 'return strlen($arg0) > 0 ? true : false;', '_CITY_REQUIRED', '', '', '', 1, '3,25', '', '', 'none', 0, 0, '', 1, '-1', '', 'Country', 'none', '5', '', '');
INSERT INTO AgentsDesc VALUES (29, 'Email,Email1', '_E-mail', 'MUST_BE_VALID', '40', 'c', 29.5, 1001, 'single', 'agent,adm', 'agent,adm', 'return (eregi("^[.0-9a-z-]+@([0-9a-z][0-9a-z-]+.)+[a-z]{2,4}$", $arg0) && !strcmp($arg0,$_POST[Email2]) && conf_email($arg0,$_COOKIE[memberID])) ? true : false;', '_EMAIL_INVALID', '', '', '', 1, '3', '', '', 'none', 0, 0, '', 0, '', '', '', 'none', '', '5', '128');
INSERT INTO AgentsDesc VALUES (31, 'Email,Email2', '_Confirm E-mail', '_MUST_BE_VALID', '40', 'c', 32, 1003, 'single', 'agent,adm', 'agent,adm', '', '', '', '', '', 0, '3', '', '', 'none', 0, 0, '', 0, '', '', '', 'none', '', '', '');
INSERT INTO AgentsDesc VALUES (32, 'HomePage', '_Homepage', '_HomePage_desc', '40', 'c', 0, 2070, 'single', 'user,agent,adm', 'agent,adm', 'return strlen($arg0) > 0 ? true : false;', '_HomePage_err_msg', '', '', '', 1, '3', '', '', 'none', 0, 0, '', 0, '', '', '', 'none', '', '', '');
INSERT INTO `AgentsDe
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200分，接分快乐
mysql> select 0&3,1&3,2&3,3&3,4&3,5&3,6&3,7&3,8&3,9&3;
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
¦ 0&3 ¦ 1&3 ¦ 2&3 ¦ 3&3 ¦ 4&3 ¦ 5&3 ¦ 6&3 ¦ 7&3 ¦ 8&3 ¦ 9&3 ¦
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
¦ 0 ¦ 1 ¦ 2 ¦ 3 ¦ 0 ¦ 1 ¦ 2 ¦ 3 ¦ 0 ¦ 1 ¦
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
和mod运算一样哈
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是呀，怎么能跟3做位运算呢？
一个SET对象的大小由不同的集合成员的数量决定。如果集合大小是N，对象占据(N+7)/8个字节，四舍
五入为1，2，3，4或8 个字节。一个SET最多能有64个成员。
visible set('user','memb','agent','adm') NOT NULL default 'user',
值 对应二进制
'user' 00000001
'memb' 00000010
'agent' 00000100
'adm' 00001000
3 00000011
于是 WHERE visible & 3 将筛选出
visible 为'user'或'memb'的记录
一直都用长整型存储权限位，还真没注意set类型可以多出一倍