Reject row from select if condition exists in another table

Question

I have two tables.

1. Contacts table - contact_id, contact_email, contact_name, etc
2. Opt out table - contact_email, scope of their opt out (event, company)

So one contact maybe have multiple event opt-outs but what I really care about is if they have a company wide opt out.

How do I join the data so that if a contact has a match with any row in the optout table that has a scope of "company" it will not show up in the result?

Answer 1

SELECT c.*
    FROM Contacts c
    WHERE NOT EXISTS(SELECT NULL
                         FROM OptOut o
                         WHERE c.contact_email = o.contact_email
                             AND o.scope = 'company')

This could also be done with a LEFT JOIN :

SELECT c.*
    FROM Contacts c
        LEFT JOIN OptOut o
            ON c.contact_email = o.contact_email
                AND o.scope = 'company'
    WHERE o.contact_email IS NULL

Answer 2

select * from contacts where contact_email not in (select contact_email from optout where scope = 'company');