SQL Query to Find Multiple Rows with Same Column Value

Question

I have a users table with a column called email and a column called enabled. I'm looking to find all users with the same email. If one of these users has enabled as nil, I would like to reset that user's login to its first name (another column). Note: There should be at most two users that share an email.

I'm just starting to learn SQL. How would I get this query working? I appreciate the patience!

update users
set users.login = users.first_name
from users u1 inner join users u2
on u1.email = u2.email 
  where u1.id != u2.id
  and u2.enabled is null

My RDBMS is MySQL!

Answer 1

If your are using MySQL then;

update users u1 
join users u2 on
u1.email = u2.email and u1.enable is null
set u1.login = u1.first_name

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