[NATIONAL] CHAR[(M)] [CHARACTER SET charset_name] [COLLATE
collation_name]

A fixed-length string that is always right-padded with spaces to the
specified length when stored. M represents the column length in
characters. The range of M is 0 to 255. If M is omitted, the length is
1.

*Note*: Trailing spaces are removed when CHAR values are retrieved.

Before MySQL 5.0.3, a CHAR column with a length specification greater
than 255 is converted to the smallest TEXT type that can hold values of
the given length. For example, CHAR(500) is converted to TEXT, and
CHAR(200000) is converted to MEDIUMTEXT. However, this conversion
causes the column to become a variable-length column, and also affects
trailing-space removal.

In MySQL 5.0.3 and later, a CHAR length greater than 255 is illegal and
fails with an error:

mysql> CREATE TABLE c1 (col1 INT, col2 CHAR(500));
ERROR 1074 (42000): Column length too big for column 'col' (max = 255);
use BLOB or TEXT instead

URL: http://dev.mysql.com/doc/refman/5.0/en/string-type-overview.html

