Oracle 5.0 Reference Manual page 349

myisamchk
•
Len
How long this portion of the index is. For packed numbers, this should always be the full length of the
column. For strings, it may be shorter than the full length of the indexed column, because you can
index a prefix of a string column. The total length of a multiple-part key is the sum of the
for all key parts.
•
Index
Whether a key value can exist multiple times in the index. Possible values are
(multiple).
•
Type
What data type this portion of the index has. This is a
packed, stripped, or empty.
•
Root
Address of the root index block.
•
Blocksize
The size of each index block. By default this is 1024, but the value may be changed at compile time
when MySQL is built from source.
•
Rec/key
This is a statistical value used by the optimizer. It tells how many rows there are per value for this
index. A unique index always has a value of 1. This may be updated after a table is loaded (or
greatly changed) with
The last part of the output provides information about each column:
•
Field
The column number.
•
Start
The byte position of the column within table rows.
•
Length
The length of the column in bytes.
• Nullpos,
Nullbit
For columns that can be NULL,
how many nullable columns there are, there can be one or more bytes used for this purpose. The
and
Nullpos Nullbit
whether the column is NULL.
The position and number of bytes used to store
there are six
Field
•
Type
The data type. The value may contain any of the following descriptors:
•
constant
All rows have the same value.
— MyISAM Table-Maintenance Utility
-a. If this is not updated at all, a default value of 30 is given.
myisamchk
stores
MyISAM
values, if nonempty, indicate which byte and bit contains that flag indicating
lines for the table even though it has only five columns.
person
329
data type with the possible values
MyISAM
values as a flag in a byte. Depending on
NULL
flags is shown in the line for field 1. This is why
NULL
values
Len
or
unique multip.