Some options are “boolean” and control behavior
that can be turned on or off. For example, the
mysql client supports a
--column-names option that
determines whether or not to display a row of column names at
the beginning of query results. By default, this option is
enabled. However, you may want to disable it in some instances,
such as when sending the output of mysql into
another program that expects to see only data and not an initial
To disable column names, you can specify the option using any of these forms:
prefixes and the
=0 suffix all have the same
effect: They turn the option off.
The “enabled” form of the option may be specified in any of these ways:
FALSE are also
recognized for boolean options (not case-sensitive).
If an option is prefixed by
--loose, a program
does not exit with an error if it does not recognize the option,
but instead issues only a warning:
$> mysql --loose-no-such-option
mysql: WARNING: unknown option '--loose-no-such-option'
--loose prefix can be useful when you run
programs from multiple installations of MySQL on the same
machine and list options in an option file. An option that may
not be recognized by all versions of a program can be given
--loose prefix (or
loose in an option file). Versions of the
program that recognize the option process it normally, and
versions that do not recognize it issue a warning and ignore it.
--maximum prefix is available for
mysqld only and permits a limit to be placed
on how large client programs can set session system variables.
To do this, use a
--maximum prefix with the
variable name. For example,
--maximum-max_heap_table_size=32M prevents any
client from making the heap table size limit larger than 32M.
--maximum prefix is intended for use with
system variables that have a session value. If applied to a
system variable that has only a global value, an error occurs.
For example, with
server produces this error:
Maximum value of 'back_log' cannot be set