mysql:int 类型的最大值问题

Question

我使用 mysql 创建了两个字段 text(varchar), number(int)。但我不确定我应该为 varchar()、int() 和 varchar() 设置什么大小，我在这里检查过:http://dev.mysql.com/doc/refman/5.0/en/char.html ，并且知道如果我输入 varchar(4)，这意味着:最多可以容纳 4 个字符。但是对于int(4)，我这里查了:http://dev.mysql.com/doc/refman/5.0/en/integer-types.html，据说是:Maximum Value:(Signed/Unsigned)(2147483647/4294967295)

问题:

对于int(4)，它是如何得到这个值2147483647/4294967295的？如果我输入 int(8)，值会是多少？

Answer 1

See the MySQL Numeric Type Documentation .这些事情都有据可查。

The range for a signed INT is [-2147483648, 2147483647].

Note that in the case of INT(x), x is the "display width" and has nothing to do with the range or space requirements:

MySQL supports an extension for optionally specifying the display width of integer data types in parentheses following the base keyword for the type. For example, INT(4) specifies an INT with a display width of four digits ... display width does not constrain [or expand] the range of values that can be stored in the column.

Mysql int(11) number out of range