php - What is the difference (when being applied to my code) between INT(10) and INT(12)?

Question

If I use INT(12) vs INT(10) or INT(8) what will this actually do in terms of me using in code?

(This is a spin off of a previous question) I read through the manuals and I think I understand what they're saying, but I don't actually know how it would apply to my php/mysql coding.

Can someone provide an example of where this would actually matter?

Answer 1

The argument to integer types in MySQL has no effect on the storage of data or the range of values supported by each data type.

The argument only applies to display width, which may be used by applications as Jonathan Fingland mentions. It also comes up when used in combination with the ZEROFILL option:

CREATE TABLE foo (
  i INT(3) ZEROFILL, 
  j INT(6) ZEROFILL, 
  k INT(11) ZEROFILL
);
INSERT INTO foo (i, j, k) VALUES (123, 456, 789);
SELECT * FROM foo;

+------+--------+-------------+
| i    | j      | k           |
+------+--------+-------------+
|  123 | 000456 | 00000000789 |
+------+--------+-------------+

See how ZEROFILL makes sure the data is zero-padded to at least the number of digits equal to the integer type argument.

Without ZEROFILL, the data is space-padded, but since spaces are often trimmed anyway, it's harder to see that difference.

What affect does it have on your PHP code? None. If you need to output columnar data, or space-pad or zero-pad values, it's more flexible to use sprintf(),