7 When the last instance of a table is closed (because of a FLUSH or because there isn't
any point.
7 To avoid problems with interaction with other processes that may do a check on the
7 MySQL has crashed between an update and the final close. (Note that the table may
(even if you will get the warning from other servers), but REPAIR should be avoided
as it currently replaces the datafile with a new one, which is not signaled to the other
servers.
reasonable stable.
A MERGE table (also known as a MRG_MyISAM table) is a collection of identical MyISAM tables
that can be used as one. You can only SELECT, DELETE, and UPDATE from the collection of
tables. If you DROP the MERGE table, you are only dropping the MERGE specification.
Note that DELETE FROM merge_table used without a WHERE will only clear the mapping for
the table, not delete everything in the mapped tables. (We plan to fix this in 4.1).
With identical tables we mean that all tables are created with identical column and key
information. You can't merge tables in which the columns are packed differently, doesn't
have exactly the same columns, or have the keys in different order. However, some of the
tables can be compressed with myisampack. See Section 4.8.4 [myisampack], page 320.
When you create a MERGE table, you will get a `.frm' table definition file and a `.MRG' table
list file. The `.MRG' just contains a list of the index files (`.MYI' files) that should be used as
one. Before 4.1.1 all used tables had to be in the same database as the MERGE table itself.
For the moment, you need to have SELECT, UPDATE, and DELETE privileges on the tables you
map to a MERGE table.
MERGE tables can help you solve the following problems:
to use these as one.
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