MyISAM supports three different storage
formats. Two of them, fixed and dynamic format, are chosen
automatically depending on the type of columns you are using. The
third, compressed format, can be created only with the
myisampack utility (see
Section 4.6.5, “myisampack — Generate Compressed, Read-Only MyISAM Tables”).
When you use CREATE TABLE or
ALTER TABLE for a table that has no
BLOB or
TEXT columns, you can force the
table format to FIXED or
DYNAMIC with the ROW_FORMAT
table option.
See Section 12.1.14, “CREATE TABLE Syntax”, for information about
ROW_FORMAT.
You can decompress (unpack) compressed MyISAM
tables using myisamchk
--unpack; see
Section 4.6.3, “myisamchk — MyISAM Table-Maintenance Utility”, for more information.