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I have a mysql table users.
A column named Email contains NULL value.
I’m not able to create a unique key on email. It is showing an error saying duplicate value ''.
That’s because you have multiple records on the email column with the value empty:
''If you use InnoDB you can have multiple
NULLvalues, but you can not have multiple empty values''.Try to clean the empty values with
UPDATE users SET email = NULL WHERE email = ''and then create the unique key.