SQL to transform all email addresses in my DB in lowercase [closed]

This is probably what you want:

update wp_users set user_email = lower(user_email) where user_email is not null;

However I’m surprised you need this: WordPress’s default collation is case-insensitive.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)