T-SQL: How to Select Values in Value List that are NOT IN the Table?

Question

I have a list of e-mail addresses, some of them are in my table, some of them are not. I want to select all e-mails from that list and whether they are in the table or not.

Answer 1

You should have a table with the list of emails to check. Then do this query:

SELECT E.Email, CASE WHEN U.Email IS NULL THEN 'Not Exists' ELSE 'Exists' END Status
FROM EmailsToCheck E
LEFT JOIN (SELECT DISTINCT Email FROM Users) U
ON E.Email = U.Email