Compare strings by case
Here’s one method of comparing strings by case in MySQL. You can use the
md5 function to hash the string and compare to its lower case value.
This example is for checking for usernames that are not lower case in moodle.
select username, md5(username), md5(lower(username)) from mdl_user where deleted = 0 and suspended = 0 and md5(username) != md5(lower(username));
md5 hash when the string is lower cased is different to the current md5 hash it will be returned and indicates a mismatch.
md5 hash is also handy when comparing values that might have invisible characters in them.