• Rec/key • Field • Start • Length • Nullpos ,  Nullbit • Type • constant • no endspace • no endspace, not_always • no endspace, no empty • table-lookup • zerofill( N ) 575 The column was converted to an  ENUM . Do not store endspace. Do not store empty values. Do not store endspace. Do not store endspace and do not do endspace compression for all values. All rows have the same value. The data type. The value may contain any of the following descriptors: For columns that can be  NULL ,  MyISAM  stores  NULL  values as a flag in a byte. Depending on how many nullable columns there are, there can be one or more bytes used for this purpose. The  Nullpos and  Nullbit  values, if nonempty, indicate which byte and bit contains that flag indicating whether the column is  NULL . The position and number of bytes used to store  NULL  flags is shown in the line for field 1. This is why there are six  Field  lines for the  person  table even though it has only five columns. The length of the column in bytes. The byte position of the column within table rows. The column number. The last part of the output provides information about each column: 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  myisamchk -a . If this is not updated at all, a default value of 30 is given. 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. myisamchk — MyISAM Table-Maintenance Utility