MySQL-大小VARCHAR [英] MySql - size VARCHAR

问题描述

许多人对我说，设置VARCHAR(100)没有意义.和255一样.我想知道为什么...

Many people say to me that set VARCHAR(100) doesnt make sense. It the same as put 255. I'd like to know why...

推荐答案

那是垃圾.他们可能在谈论varchar使用一个字节作为长度的事实，而不管最大长度是100还是255(超过该长度将使用两个字节，最大为〜64K)，但是它们是区别对待.

That's rubbish. They may be talking about the fact that a varchar uses one byte for the length regardless of whether the maximum length is 100 or 255 ( lengths above that will use two bytes, up to ~64K) but they are treated differently.

如果在前者中插入一个150个字符的字符串，它将被截断为100，对于后一种情况并非如此.

If you insert a 150-character string into the former, it will be truncated to 100, that's not so for the latter case.

您应该使用有意义的长度.如果您有一列不超过30个字符的列，请不要使用varchar(255).

You should use the length that makes sense. If you have a column that will never exceed 30 characters, don't use varchar(255).

有关类型的详细信息，请参见此处.

See here for the type details.

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