If any column in a table has a variable length, the entire row becomes
variable-length as a result. Therefore, if a table contains any
variable-length columns (VARCHAR, TEXT, or BLOB), all CHAR columns
longer than three characters are changed to VARCHAR columns. This
doesn't affect how you use the columns in any way; in MySQL, VARCHAR
is just a different way to store characters. MySQL performs this
conversion because it saves space and makes table operations faster.
See section 15 MySQL Storage Engines and Table Types.
Does this affect all table types? I'm curious if this is happening on
my InnoDB tables as well. No problems, just curiosity..