asking comment

Hello, I got a bit frustrated with image upload stuff with different image name problems. So I created a system that gives the uploaded imaged a random numeric name between 1-10 000 000 and saves the file to a server folder and the image name to mysql DB. Is there a so sort of a problem here that I am not thinking of? I only can imagine problem that the rand() gives the same value twice. But I cant see this as a major problem because there would be maybe not more than 1000 uploaded pictures. So the chance is at worst something like 1:10 000 that same name is created to the image. Anyway if same name is created what's the best way to check that? I was thinking of putting the image name field in DB as a unique field. That would do it? Right? Thanks again -Will