MYSQL优化'IN'和'ORDER BY'

EXPLAIN 
    SELECT * FROM test_askcomment WHERE cid IN(1,2,3) ORDER BY dateline DESC;

id select_type表类型possible_keys key key_len ref行额外1 SIMPLE test_askcomment ALL PRIMARY NULL NULL NULL 3使用where; 使用filesort

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ALTER TABLE `test_askcomment ` ADD INDEX `index1` (`cid`);

ALTER TABLE `test_askcomment ` ADD INDEX `index2` (`dateline `);

尝试为您使用where子句或选择coloumns的coloumns编制索引

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