varchar(255) is not a form of encryption, it is a data type and length. Can you provide additional information?
I have a field on SQL, its password for user which use varchar(255) and it look like this e10adc3949ba59abbe56e057f20f883e I want to convert it to plain text, is it possible?
It depends on the form of encryption. Is this a custom, open-source, or commercial application? The string you posted could be a MD5 hash; do you know what type of encryption is used?
You would need to look at the application and see how the password is inserted. Most likely it is a hash, and cannot be decrypted. Normally you would use char 32 (at least for MD5) but a varchar field would work fine, although not ideal. If it is a hash, there is no way to decode it. You can only update the value in that field.
The idea with password hashes is that they're one way only, which essentially means that you can't decrypt it. Now, you might be able to find a collision, but that is probably more technically involved than you'd like. And even then, you probably wouldn't get the password, but instead only a string that has the same hash. The best idea for you, depending on what you're trying to do, is to create an MD5 hash of a password you want to use, and replace THAT value with the new hash. Here's a site that'll work for you: http://www.xs4all.nl/~jlpoutre/BoT/Javascript/Utils/md5_hashing.html Something to also consider is the possible use of a salt, which would just throw an extra wrench in your cogs.