Oracle 5.0 Reference Manual page 1058

When packing binary number keys, MySQL uses prefix compression:
• Every key needs one extra byte to indicate how many bytes of the previous key are the same for
the next key.
• The pointer to the row is stored in high-byte-first order directly after the key, to improve
compression.
This means that if you have many equal keys on two consecutive rows, all following "same" keys
usually only take two bytes (including the pointer to the row). Compare this to the ordinary case
where the following keys takes
size is usually 4). Conversely, you get a significant benefit from prefix compression only if you have
many numbers that are the same. If all keys are totally different, you use one byte more per key, if
the key is not a key that can have
same byte that is used to mark if a key is NULL.)
•
PASSWORD
This option is unused. If you have a need to scramble your
any other MySQL server, please contact our sales department.
•
ROW_FORMAT
Defines how the rows should be stored. For
for static or variable-length row format.
DYNAMIC
Section 14.1.3, "MyISAM
Starting with MySQL 5.0.3, for
(ROW_FORMAT=COMPACT) by default. The noncompact format used in older versions of MySQL can
still be requested by specifying ROW_FORMAT=REDUNDANT.
Note
When executing a
which is not supported by the storage engine that is used for the table,
the table is created using that storage engine's default row format. The
information reported in this column in response to
is the actual row format used. This may differ from the value in the
Create_options
retained during creation.
•
RAID_TYPE
support has been removed as of MySQL 5.0.
RAID
•
UNION
is used when you want to access a collection of identical
UNION
only with tables. See
MERGE
You must have
SELECT
a table.
MERGE
Note
Formerly, all tables used had to be in the same database as the
itself. This restriction no longer applies.
CREATE TABLE
storage_size_for_key + pointer_size
values. (In this case, the packed key length is stored in the
NULL
MyISAM
Table Storage Formats".
tables, rows are stored in compact format
InnoDB
CREATE TABLE
column because the original
Section 14.3, "The
[578], [578], and
UPDATE
1038
Syntax
files and make them unusable to
.frm
tables, the option value can be
sets the type to COMPRESSED. See
myisampack
statement, if you specify a row format
SHOW TABLE STATUS
CREATE TABLE
MyISAM
Storage Engine".
MERGE
[577] privileges for the tables you map to
DELETE
(where the pointer
or
FIXED
definition is
tables as one. This works
table
MERGE