(PHP 4, PHP 5)
sybase_select_db — Selects a Sybase database
sybase_select_db() sets the current active database on the server that's associated with the specified link identifier.
Every subsequent call to sybase_query() will be made on the active database.
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.
成功时返回 TRUE， 或者在失败时返回 FALSE.