MYSQL: UNSIGNED vs SIGNED

Source: https://stackoverflow.com/questions/11515594/when-should-i-use-unsigned-and-signed-int-in-mysql

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

UNSIGNED ranges from 0 to n, while signed ranges from about -n/2 to n/2.

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).