什么时候应该在MySQL中使用UNSIGNED和SIGNED INT? [英] When should I use UNSIGNED and SIGNED INT in MySQL?

问题描述

何时应在MySQL中使用UNSIGNED和SIGNED INT? 使用哪种更好，或者这只是个人偏爱? 因为我看过它像这样使用；

When should I use UNSIGNED and SIGNED INT in MySQL ? What is better to use or this is just personal prefernce ? Because I've seen it used like this;

id INT(10) UNSIGNED NOT NULL AUTO_INCREMENT

和

id INT(11) NOT NULL AUTO_INCREMENT

推荐答案

UNSIGNED仅存储正数(或零).另一方面，已签名可以存储负数(即，可以具有负 ).

UNSIGNED only stores positive numbers (or zero). On the other hand, signed can store negative numbers (i.e., may have a negative sign).

这是每个INTEGER类型可以存储的值范围的表:

Here's a table of the ranges of values each INTEGER type can store:

^{来源: http://dev.mysql.com/doc/refman/5.6/en/integer-types.html}

^{Source: http://dev.mysql.com/doc/refman/5.6/en/integer-types.html}

UNSIGNED的范围从0到 n ，而有符号的范围从大约-n/2到n/2.

在这种情况下，您有一个AUTO_INCREMENT ID列，因此您没有负数.因此，请使用UNSIGNED.如果在AUTO_INCREMENT列中不使用UNSIGNED，则最大可能值将是最大值的一半(并且值范围的负一半将不使用).

In this case, you have an AUTO_INCREMENT ID column, so you would not have negatives. Thus, use UNSIGNED. If you do not use UNSIGNED for the AUTO_INCREMENT column, your maximum possible value will be half as high (and the negative half of the value range would go unused).

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