Question

I have a table users. I wish to update the column email based on some condition only.

update users set email='$email' where uid='$uid' 

(I wish to update the table users only if there is no other record containing the same email id)

Answer 1

While creating the table you need to make the email coloumn as an unique such that it will not allow you to insert duplicate values.Now you can use the above query such that there will be no email repeated in the table email coloumn