如何导出动态生成的临时csv文件？

I would like to generate a csv file with data, that I get by querying a database. The browser then should prompt the user to download the file. By problem is, that the readfile function needs a filename and not a handle, but I can't find a function to get the filename of this temporary file. I guess there are better ways to do this, but I can't find them.I would like to generate a csv file with data,