2.13.4 Rebuilding or Repairing Tables or Indexes  This section
describes how to rebuild a table. This can be necessitated by
changes to MySQL such as how data types are handled or changes
to character set handling. For example, an error in a collation
might have been corrected, necessitating a table rebuild to
update the indexes for character columns that use the collation.
(For examples, see Section 2.13.3, “Checking Whether Tables or
Indexes Must Be Rebuilt”.) It might also be that a table repair
or upgrade should be done as indicated by a table check
operation such as that performed by CHECK TABLE, mysqlcheck, or
mysql_upgrade.  Methods for rebuilding a table include dumping
and reloading it, or using ALTER TABLE or REPAIR TABLE.
shell> mysqldump db_name t1 > dump.sql shell> mysql db_name <
dump.sql   shell> mysqldump db_name > dump.sql shell> mysql
db_name < dump.sql   shell> mysqldump --all-databases > dump.sql
shell> mysql < dump.sql  To rebuild a table with ALTER TABLE,
use a null alteration; that