成功回傳TRUE失敗回傳FALSE。
mysql_select_db() sets the
current active database on the server that's associated with
the specified link identifier. If no link identifier is
specified, the last opened link is assumed. If no link is
open, the function will try to establish a link as if
mysql_connect() was called without arguments, and use
it.
Every subsequent call to
mysql_query() will be made on the active
database.
See also: mysql_connect(),
mysql_pconnect(), and
mysql_query().
For downward compatibility
mysql_selectdb() can also be used. This is deprecated
however.