How to concatenate columns properly using T-SQL?

Question

I have a address in more than one column in a table.

SELECT FirstName, LastName, StreetAddress, City, Country, PostalCode 
FROM Client

I a

Answer 1

Look at isnull

You can also look at using COALESCE function, please look it up in BOL:

Returns the first nonnull expression among its arguments.

Finally another thing you could do is use a CASE function.

SELECT Address1, CASE Address2 IS NOT NULL THEN "," + Address2 ELSE...