the top half——already exists是什么意思

the record already exists什么意思 请问“A file with that name already exists”是什么意思? The Cell Definition already exists in this or another worksh “top—notch”是什么意思? exists是什么意思 cover the top half of this pic half way down from the top I have read half the book already the top student是什么意思 “An account already exists with that E-mail address,and the 英语翻译cover the top half of this pic oracle中EXISTS是什么意思