如题
CREATE TABLE `score` ( `id` int(11) NOT NULL, `studentid` int(11) NOT NULL, `subjectid` int(11) NOT NULL, `score` int(11) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; -- 新建一个索引能够同时提升三条SQL的查询性能 ALTER TABLE `score` ADD INDEX `score` ( `score` , `studentid` , `subjectid` ) EXPLAIN SELECT * FROM score WHERE score=100; EXPLAIN SELECT * FROM score WHERE studentid=5 AND score=100; EXPLAIN SELECT * FROM score WHERE studentid=5 AND subjectid=2 AND score=100;
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