yellowpepper https://blog.hatena.ne.jp/yellowpepper/ Log4jpnLog https://yellowpepper.hatenadiary.org/ MySQL explain SELECT ~~ もしくは desc SELECT ~~ これで調べられる.possible_keys は候補の鍵, key は実際に使われている鍵. mysql> explain select id from data where id=10102 and flg!=2; + id select_type table type possible_keys key key_len ref rows Extra + 1 SIMPLE user_card ref PRIMARY,i2 PRIMARY 4 const 18 Using where + 1 row in set (0… 190 <iframe src="https://hatenablog-parts.com/embed?url=https%3A%2F%2Fyellowpepper.hatenadiary.org%2Fentry%2F20120722%2F1342963040" title="MySQLでインデックスが効いているか確かめる方法 - Log4jpnLog" class="embed-card embed-blogcard" scrolling="no" frameborder="0" style="display: block; width: 100%; height: 190px; max-width: 500px; margin: 10px 0px;"></iframe> Hatena Blog https://hatena.blog 2012-07-22 22:17:20 rich https://yellowpepper.hatenadiary.org/entry/20120722/1342963040 1.0 100%