轻松掌握MySQL中静态（固定长度）表特征

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轻松掌握MySQL中静态（固定长度）表特征_MySQL

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Jun 01, 2016 pm 01:55 PM

storagesurface

　　静态格式是MyISAM表的默认存储格式。当表不包含变量长度列（VARCHAR, BLOB, 或TEXT）时，使用这个格式。每一行用固定字节数存储。

　　MyISAM的三种存储格式中，静态格式就最简单也是最安全的（至少对于崩溃而言）。静态格式也是最快的on-disk格式。快速来自于数据文件中的行在磁盘上被找到的容易方式：当按照索引中的行号查找一个行时，用行长度乘以行号。同样，当扫描一个表的时候，很容易用每个磁盘读操作读一定数量的记录。

　　当MySQL服务器正往一个固定格式MyISAM文件写的时候，如果计算机崩溃了，安全是显然的。在这种情况下，myisamchk可以容易地决定每行从哪里开始到哪里结束，所以它通常可以收回所有记录，除了写了一部分的记录。注意，基于数据行，MyISAM表索引可以一直被重新构建。

　　静态格式表的一般特征：

　　? CHAR列对列宽度是空间填补的。

　　? 非常快。

　　? 容易缓存。

　　? 崩溃后容易重建，因为记录位于固定位置。

　　? 重新组织是不必要的，除非你删除巨量的记录并且希望为操作系统腾出磁盘空间。为此，可使用OPTIMIZE TABLE或者myisamchk -r。

　　? 通常比动态格式表需要更多的磁盘空间。

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