MS SQL IF ELSE condition checking

[Yas]

Hello,

I have Table1 with column Email, which has mail addresses in the
format 'useremailid@'. Few of these Email values are NULL where no
mail address was specified.

In my View1 I'm using SUBSTRING like... Left(Email,CHARINDEX('@',
Email)-1) AS EMAIL_NAME (to cut out the @ sign) FROM Table1 and get
just the usermailid

Anyway, what I would like to do is use the above to get all the
usermailids and have a condition that checks if Email field IS NULL
and if TRUE replaces it with blank value ''

So something like IF (Email IS NULL) THEN Email = ''

I've never really used IF ELSE in a query and would be gratefull if
someone could help me out. I don't want to leave out the NULL values
using WHERE Email is NOT NULL, I just want to convert them to an empty
string ''

Many thanks in advance :-)

Yas