8 replies to this topic

[engr]

Hi All,
I am uploading images to SQL Server 2005 using asp.net. The database table has a binary field, image length field,file path field and a field for the file type.

The issue is that the user is able to upload the same image to the database using different file names.

What unique property should I check for to prevent duplicate images from being uploaded. I tried checking the file length but two different images can have the same length, so this prevented a new image from being uploaded.

Anyone has any idea?

Thanks in advance

Edited by engr, 03 June 2009 - 01:48 AM.
Indicative Subject

[WingedPanther]

There isn't going to be an efficient way to do this. Worse, the user uploading the duplicate image may not know it's a duplicate under a different file name and could be irritated at being blocked.

[engr]

So tell me the inefficient way :)

[WingedPanther]

Open each binary field and compare it with the one to be saved :)

[engr]

if i run this query on the database table -
select hashbytes('md5',cast(picture as varbinary(max))) from tblPicture

it gives the error of 'String or binary data would be truncated'.

I was thinking of comparing the input image against each image in the database by hashing it.

Any solutions???

[WingedPanther]

When you save an image, you could have a hash field and a length field. That should give you a pretty good indicator. Then you can do a "SELECT COUNT(*) FROM tblPicture WHERE HASH='value' AND LENGTH=length". IF the count is 0, go ahead and insert.

[Orjan]

sounds in my ears as the probably best option, WP

[engr]

But as I said hashing the image field gives an error of 'Binary field would be truncated'.

Is there another way of hashing?

[WingedPanther]

It sounds like you don't have a wide enough field to store the hash? Where exactly are you getting the error?