[rightinpoint]

Just wonder, what means have number M at the field declaration like
field_name INT(M) ?

I have used to use it as length in bytes, mannual claim, that

M indicates the maximum display width for integer types

, but simple tests doesn't show any difference between int(1), int(3), int(5), int(11).

So basically, what does that number mean?

[guelphdad]

Gee it's like you found all the mysql forums today. ;-)
See this item

[ortho]

I think that the M digit, is only used for the ZEROFILL parameter, so if you do not use the zerofill, you should only use INT or INT(11) wich is the default.

NB: You better validate this info, I'm not sure about it.

[ortho]

CREATE TABLE testTable (
`a` INT(11),
`b` INT(11) ZEROFILL
);
INSERT INTO testTable (`a`, `b`) VALUES (1, 1);
SELECT * FROM testTable;

With this Query you should see the difference

[rightinpoint]

thank you guys for the your help, all is clear for me now

[guelphdad]

INT(11) is not the default INT is. Any GUI that automatically assigns a length value to numeric data types is doing so incorrectly and really gives people the wrong idea about what values can be held in the data type.

[ortho]

but if I specify INT as a datatype in mySql, and then I export the table, it will export my INT field as INT(11)...

[aschk]

As you rightly quoted from the MySQL manual :

M indicates the maximum display width for integer types

This means that any integer number that displays BELOW this width (as example: 4) will be padded with spaces (or if zerofill specified 0's) ,

CREATE TABLE testTable (
`a` INT(4),
`b` INT(4) ZEROFILL
);
INSERT INTO testTable (`a`, `b`) 
VALUES (1, 1)
      ,(12,12)
      ,(123,123)
      ,(1234,1234)
      ,(12345,12345);

will actually be producing :

   a  ||   b
=============
    1 || 0001
   12 || 0012
  123 || 0123
 1234 || 1234
12345 || 12345

note in column `a` you have 3,2,1,0,0 spaces in front of your number