MySQL查询优化:LIMIT 1避免全表扫描-白红宇的个人博客

发布日期：2025-04-17 23:57:49 浏览次数：52 分类：精选文章

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????????????????????SQL?????LIMIT 1??????????????????

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SELECT * FROM t_user WHERE email='222@xxg.com';

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??LIMIT 1???

???????????????LIMIT 1????

SELECT * FROM t_user WHERE email='222@xxg.com' LIMIT 1;

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?????????????????????????LIMIT 1????

SELECT * FROM t_user WHERE id=?;

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BEGIN  DECLARE i INT;  START TRANSACTION;  SET i = 0;  WHILE i < 1000000 DO    INSERT INTO t_user VALUES (NULL, CONCAT(i + 1, '@xxg.com'), i + 1);    SET i = i + 1;  END WHILE;  COMMIT;END

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SELECT * FROM t_user WHERE email='222@xxg.com'; ???0.56?

SELECT * FROM t_user WHERE email='222@xxg.com' LIMIT 1; ???0.00?

???????LIMIT 1????????????

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