varchar字段 - 两个更有效率的力量？ [英] varchar Fields - Is a Power of Two More Efficient?

问题描述

使用两个与另一个数字的幂的varchar字段是否更有效？我在想，不，因为SQL Server的默认值为50.但是，我已经听到（但从来没有确认过），将大小字段设置为2的大小更有效率，因为它们等同于偶数字节，并且计算机处理位数;字节。那么，声明为varchar（32）还是varchar（64）的字段对varchar（50）有任何真正的好处吗？

Is it more efficient to use a varchar field sized as a power of two vs. another number? I'm thinking no, because for SQL Server the default is 50. However, I've heard (but never confirmed) that sizing fields as a power of 2 is more efficient because they equate to even bytes, and computers process in bits & bytes. So, does a field declared as varchar(32) or varchar(64) have any real benefit over varchar(50)?

推荐答案

no。

在某些其他用途中，使用具有两个大小的结构的结构有一些优势，主要是因为您可以适合一个好的（两个数量）的数字这些都在另一个两尺寸的结构中。但是这不适用于DB fieldsize。

in some other uses, there are some advantages to use structures with a power of two size, mostly because you can fit a nice (power of two) number of these inside another power-of-two-sized structure. but this doesn't apply to a DB fieldsize.

与VARCHAR相关的唯一的二次调整大小是关于varchar（或TEXT / BLOB）的确切类型在某些SQL方言中）：如果小于256，则可以使用单个字节来指示长度。如果小于65536（64KB），两个字节就足够了，三个字节可以达到16777216（16MB），四个字节可以转到4294967296（4GB）。

the only power-of-two-sizing related to VARCHARs is about the exact type of varchar (or TEXT/BLOB in some SQL dialects): if it's less than 256, it can use a single byte to indicate length. if it's less than 65536 (64KB), two bytes are enough, three bytes work up to 16777216 (16MB), four bytes go to 4294967296 (4GB).

可以认为， VARCHAR（50）与$ code> VARCHAR（255）一样贵，因为两者都需要n +1字节的存储空间。

also, it can be argued that VARCHAR(50) is just as expensive as VARCHAR(255), since both will need n+1 bytes of storage.

当然这是在思考Unicode ...

of course that's before thinking of Unicode...

这篇关于varchar字段 - 两个更有效率的力量？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！