Question

So I want to select all users where username is contained in the email

for instance in this username – email table

mee - [e-mail]
mee2 - [e-mail]
mee3 - [e-mail]
jft - [e-mail]
uey - [e-mail]

I want to only return mee, mee3, jft and uey where the username is contained in the email – now how do I do that?

I Could use Brian Hoovers solution, but I actually chose the following where clause

where email = CONCAT(`username`, '@unregistered.com')

Answer 1

select username, substring(email, 1, locate('@', email)- 1) from usertable
where lower(username) = lower(substring(email, 1, locate('@', email)- 1));

This would give you every email where the username and the beginning of the email are the same