CASE Statement in SQL Server to get output I need - sql-server

Question

So a friend of mine told me to check the almost 5 million email addresses that got 'Hacked' on Gmail.
I downloaded the file a text file, with almost 5 million emails (4804288). I figured I'd just open it in my text editor and Ctrl+F my email address. Well it took forever to just open the .txt document and it crashed. I then exported it to Excel but it has a limit of 1 million+ rows. Since I'm studying SQL I figured I'll just load it into SQL Server and query it creating a stored procedure. It should be cool.
So.. what did I do?
Created a table called 5Mil.
And bulk inserted the info from the .txt file:
BULK INSERT [dbo].[5Mil]
FROM 'C:\list\google.txt'
WITH (fieldterminator = ',', rowterminator = '#gmail.com')
GO
First question, since the txt file had one line per email without a ',' at the end the only way I could load the info was using the rowterminator = '#gmail.com' which truncated '#gmail.com' and left only the username part of the email.
Maybe someone can help me understand how to import the information including the #gmail.com.
I was able to import the email addresses 1 per row. total rows 4804288.
So far so good.
I am currently learning CTE's so I figured I'd apply this to my stored procedure.
This is what I did.
CREATE PROC googlemails
#email VARCHAR(MAX)
AS
WITH CTE AS
(
SELECT Emails
FROM dbo.[5Mil]
WHERE Emails LIKE '%'+#email+'%'
)
SELECT
CASE
WHEN Emails IS NOT NULL
THEN Emails
ELSE 'you are safe'
END AS 'Google Email'
FROM CTE
When I run the procedure and it finds emails it properly lists them.
But when I put an email address that's not in the list I get
Google Email
Blank. What I want is to be able to show 'You are safe' letting the user know that your email was not part of the 5 Mill 'hacked'.
What would be the proper way to use the CASE statement here. Or like always other ways of accomplishing this task. For learning purposes.
Thank you.

Answer 1

select case when exists( select 1 from 5MIL WHERE Emails LIKE '%'+#email+'%')
then 'hacked'
else 'not hacked' end
CTE not appropriate here; they're mostly for simplifying large queries and for recursive queries.

Answer 2

As I understand it you now have a table called 5Mil with one column called Email each with a username without the "#gmail.com". It is unnecessarily redundant to append "#gmail.com" to each one.
Soooo.... why not just search for the username part? Using a LIKE '%email%' is slow and inefficient. Much simpler to just to do this in your stored procedure (similar to dudNumber4's answer but don't use "LIKE"):
--SET #Email = 'someusername' -- note no "#gmail.com"
if EXISTS(SELECT 1 from 5Mil where Email = #Email)
SELECT 'Hacked'
ELSE
SELECT "Not hacked"
if you create an index on 5Mil.Email the search will be almost instant.