=

1. Assumed equal
2. Compared character by character
3. When the string on the right side is exhausted the result is returned

==

1. Assumed equal
2. Compared character by character
3. When the string on the right side is exhausted 
4. They are compared for length and the result is returned

SET EXACT ON

=

1. Strings are padded on the right with spaces to be of equal length
2. Assumed equal
3. Compared character by character
4. When the string on the right side is exhausted the result is returned

== exactly the same as with set exact off

SET ANSI ON/OFF acts like SET EXACT but for SELECT WHERE clauses