you can specify your column types to be several lengths:
if you use CHAR().. you can have a maximum of 255 characters (1-255, you specify)
you can specify a number of max characters, up to 255... if you make you column type TINYBLOB or
, you can have anywhere from 1-255 (2^5 - 1). BLOB or TEXT
types have a maximum of 65535 (2^16 - 1) characters. MEDIUMBLOB or MEDIUMTEXT
columns have a maximum length of 4294967295 (2^32 - 1) characters. LONGBLOB or LONGTEXT
have a maximum length of 4294967295 (2^32 - 1) characters.
those are just some of the column types. The more specific you make your colums, the more control you have over your database, and the input you get from users. For a better list.. go here