What's the difference in int(11) and int(11) UNSIGNED?

Question

What\'s the difference in int(11) and int(11) UNSIGNED ?

Answer 1

An UNSIGNED type cannot be negative, but on the other hand it has twice as large a range for the positive integers. The types TINYINT, SMALLINT, MEDIUMINT, INT and BIGINT all have signed and unsigned versions.

For INT the ranges are defined as follows:

Type          Storage         Min           Max
INT                 4 -2147483648    2147483647
INT UNSIGNED        4           0    4294967295

The signed and unsigned types take the same storage space (4 bytes for INT).

See the documentation for more details.

Answer 2

All integer types can have an optional (nonstandard) attribute UNSIGNED. Unsigned type can be used to permit only nonnegative numbers in a column or when you need a larger upper numeric range for the column. For example, if an INT column is UNSIGNED, the size of the column's range is the same but its endpoints shift from -2147483648 and 2147483647 up to 0 and 4294967295.

see here: http://dev.mysql.com/doc/refman/5.0/en/numeric-types.html

Answer 3

UNSIGNED means that it can hold only nonnegative values, i.e. it can't hold for example -20

Answer 4

I think you may want to know the difference between int and int(10).

Let's give an example for int(10) one with zerofill keyword, one not, the table likes that:

create table tb_test_int_type(
    int_10 int(10),
    int_10_with_zf int(10) zerofill,
    unit int unsigned
);

Let's insert some data:

insert into tb_test_int_type(int_10, int_10_with_zf, unit)
values (123456, 123456,3147483647), (123456, 4294967291,3147483647) 
;

Then

select * from tb_test_int_type; 

# int_10, int_10_with_zf, unit
'123456', '0000123456', '3147483647'
'123456', '4294967291', '3147483647'

We can see that

• with keyword zerofill, num less than 10 will fill 0, but without zerofill it won't

• Secondly with keyword zerofill, int_10_with_zf becomes unsigned int type, if you insert a minus you will get error Out of range value for column...... But you can insert minus to int_10. Also if you insert 4294967291 to int_10 you will get error Out of range value for column.....

Conclusion:

1. int(X) without keyword zerofill, is equal to int range -2147483648~2147483647

2. int(X) with keyword zerofill, the field is equal to unsigned int range 0~4294967295, if num's length is less than X it will fill 0 to the left

Answer 5

INT goes from -2147483648 to +2147483647
UNSIGNED INT goes from 0 to 4294967295

the 11 between the braces has no effect on the number, just how it's displayed.

Answer 6

The unsigned one can't hold negative numbers.