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我有一张这样的桌子：

CREATE TABLE `entries` (
  `n` int(10) unsigned NOT NULL DEFAULT '0',
  `title` varchar(255) NOT NULL DEFAULT '',
  `description` varchar(255) NOT NULL DEFAULT '',
  `c` char(6) DEFAULT NULL,
  `c_path` char(24) DEFAULT NULL,
  `a` char(8) DEFAULT NULL,
  `a_path` char(32) DEFAULT NULL,
  `hide_in_supercat` tinyint(1) NOT NULL DEFAULT '0',
  `created` int(10) unsigned NOT NULL DEFAULT '0',
  `edited` int(10) unsigned NOT NULL DEFAULT '0',
  `t1` int(10) unsigned NOT NULL DEFAULT '0',
  `t2` int(10) unsigned NOT NULL DEFAULT '0',
  `status` set('waiting','enabled','disabled','queue','wait','preview') NOT NULL DEFAULT '',
  `clicks_total` int(10) unsigned NOT NULL DEFAULT '0',
  `popular` tinyint(1) NOT NULL DEFAULT '0',
  `featured_until` int(10) unsigned NOT NULL DEFAULT '0',
  `home_page_until` int(10) unsigned NOT NULL DEFAULT '0',
  PRIMARY KEY (`n`,`t1`,`t2`,`status`,`en_cats`),
  KEY `category_page_index` (`c`,`c_path`,`hide_in_supercat`,`featured_until`,`highlight_until`),
  KEY `category_page_index_2` (`c`,`c_path`,`hide_in_supercat`,`featured_until`,`highlight_until`,`created`,`clicks_total`),
  FULLTEXT KEY `search` (`title`,`description`,`detail`,`keywords`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8

我正在尝试运行以下查询：

select sql_no_cache * from gc_ads where c_path in ("_9_","_9_30_","_9_101_","_9_102_","_9_103_","_9_105_","_9_106_","_9_30_132_","_9_30_133_","_9_30_134_","_9_30_135_","_9_30_136_","_9_30_137_","_9_30_138_","_9_30_139_","_9_30_140_","_9_30_141_","_9_30_142_","_9_30_143_","_9_30_144_","_9_30_145_","_9_30_146_","_9_30_147_","_9_30_148_","_9_30_149_","_9_30_150_","_9_30_151_","_9_30_152_","_9_30_153_","_9_30_154_","_9_30_155_","_9_30_156_","_9_30_157_","_9_30_158_","_9_30_159_","_9_30_160_","_9_30_161_","_9_30_162_","_9_101_222_","_9_101_221_","_9_101_220_","_9_101_219_","_9_101_218_","_9_101_217_","_9_101_216_","_9_101_215_","_9_101_214_","_9_101_213_","_9_101_212_","_9_101_211_","_9_101_210_","_9_101_209_","_9_101_208_","_9_101_207_","_9_101_206_","_9_101_205_","_9_101_204_","_9_101_203_","_9_101_202_","_9_101_201_","_9_101_200_","_9_101_199_","_9_101_198_","_9_101_196_","_9_101_197_","_9_101_195_","_9_194_","_9_101_223_","_9_101_224_","_9_101_225_","_9_102_226_","_9_102_227_","_9_102_228_","_9_102_229_","_9_102_230_","_9_102_231_","_9_102_232_","_9_102_233_","_9_102_234_","_9_102_235_","_9_102_236_","_9_102_237_","_9_102_238_","_9_102_239_","_9_102_240_","_9_102_241_","_9_102_242_","_9_102_243_","_9_102_244_","_9_102_245_","_9_102_246_","_9_102_247_","_9_102_248_","_9_102_249_","_9_102_250_","_9_102_251_","_9_102_252_","_9_102_253_","_9_102_254_","_9_102_255_","_9_102_256_") AND status = 'enabled' and (hide_in_supercat!=1 or c='_9_') order by created desc limit 0,50;

解释给了我以下信息：

    +----+-------------+--------+------+-------------------------------------------+------+---------+------+-------+-----------------------------+
| id | select_type | table  | type | possible_keys                             | key  | key_len | ref  | rows  | Extra                       |
+----+-------------+--------+------+-------------------------------------------+------+---------+------+-------+-----------------------------+
|  1 | SIMPLE      | gc_ads | ALL  | category_page_index,category_page_index_2 | NULL | NULL    | NULL | 60554 | Using where; Using filesort |
+----+-------------+--------+------+-------------------------------------------+------+---------+------+-------+-----------------------------+

我对 MySQL 和索引比较陌生，所以这没有任何意义。我敢肯定，这可能是我缺少的一些简单概念。

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