参考文献：https://segmentfault.com/a/1190000012479448
int(11)中的11代表的是字符的显示宽度，在字段类型为int时，无论你显示宽度设置为多少，int类型能存储的最大值和最小值永远都是固定的，这里贴一些原文片段
The number in the parenthesis does not determines the max and min values that can be stored in the integer field. The max and min values that can be stored are always fixed.
The display width of the column does not affects the maximum value that can be stored in that column. A column with INT(5) or INT(11) can store the same maximum values. Also, if you have a column INT(20) that does not means that you will be able to store 20 digit values (BIGINT values). The column still will store only till the max values of INT.