SQL Server: Null VS Empty String

Question

How are the NULL and Empty Varchar values stored in SQL Server. And in case I have no user entry for a string field on my UI<

Answer 1

Be careful with nulls and checking for inequality in sql server.

For example

select * from foo where bla <> 'something' 

will NOT return records where bla is null. Even though logically it should.

So the right way to check would be

select * from foo where isnull(bla,'') <> 'something' 

Which of course people often forget and then get weird bugs.