I noticed some interesting thing
When I create some field lets say of int type its size supposed to be 4 bytes. Like this

Alter table tbl_countries add country_id INT

Then I looked into the table using MySQL-Front and was amaized to find out that the field has a length of 11. From where is the addon of 7 bytes ?

If i force the size and change it to 4 it works perfectly. And the maximum value that can be in both cases is 4294967295 (unsigned) but why mysql adds those 7 bytes?

By the way the same thing is happening with tinyint which by default comes with size of 4 instead of 1.

If anyone can explain this I would be thankful.

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My second question is about alter table
I want to add pack_keys=1 to some of my read only accessed tables which have numeric indexes, what is the correct alter table statement to add this option.

Thanks