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MySQL SQL语句优化的10条建议_MySQL

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Jun 01, 2016 pm 01:18 PM

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bitsCN.com 1.将经常要用到的字段（比如经常要用这些字段来排序，或者用来做搜索），则最好将这些字段设为索引。
2.字段的种类尽可能用int 或者tinyint类型。另外字段尽可能用NOT NULL。
3.当然无可避免某些字段会用到text ,varchar等字符类型，最好将text字段的单独出另外一个表出来（用主键关联好）
4.字段的类型，以及长度，是一个很考究开发者优化功力的一个方面。如果表数据有一定的量了，不妨用PROCEDURE ANALYSE()命令来取得字段的优化建议！（在phpmyadmin里可以在查看表时，点击 “Propose table structure” 来查看这些建议）如此可以让你的表字段结构趋向完善。
5.select * 尽量少用，你想要什么字段就select 什么字段出来不要老是用* 号！同理，只要一行数据时尽量使用 LIMIT 1
6.绝对不要轻易用order by rand() ，很可能会导致mysql的灾难！！
7.每个表都应该设置一个ID主键，最好的是一个INT型，并且设置上自动增加的AUTO_INCREMENT标志，这点其实应该作为设计表结构的第一件必然要做的事！！
8.拆分大的 DELETE 或 INSERT 语句。因为这两个操作是会锁表的，表一锁住了，别的操作都进不来了，就我来说有时候我宁愿用for循环来一个个执行这些操作。
9.不要用永久链接 mysql_pconnect()；除非你真的非常肯定你的程序不会发生意外，不然很可能也会导致你的mysql死掉。
10.永远别要用复杂的mysql语句来显示你的聪明。就我来说，看到一次关联了三，四个表的语句，只会让人觉得很不靠谱。bitsCN.com

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