sybase_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
sybase_connect() was called, and use it.
成功回傳TRUE失敗回傳FALSE。
Every subsequent call to
sybase_query() will be made on the active
database.
See also: sybase_connect(),
sybase_pconnect(), and
sybase_query()