SELECT without FROM clause

SELECT 'Test1' WHERE EXISTS (SELECT 1/0)

SELECT 'Test2' WHERE EXISTS (SELECT *)

Those 2 statements won't raise an Error in SQL SERVER!

Te results will be:

Test1

Test2

Of course that SELECT 1/0 or SELECT * will raise an Error.

In SQL SERVER the FROM clause is optional. 

This is why SELECT 1 , SELECT @P and SELECT @P=5 are permitted.

In other database systems (Like Oracle), SELECT statement without FROM clause is not permitted, and there is a dummy table "DUAL" with one row that is used to do such SELECT statements:

SELECT 1 FROM dual , SELECT @v FROM dual.

Another thing is that in EXISTS clause doesn't matter in terms of the syntax or result of the query.

Those 2 facts (SELECT without FROM is allowed and EXISTS doesn't matter in terms of the syntax) 

explains the behavior of the 2 statements above.

https://connect.microsoft.com/SQLServer/feedback/details/671475/select-test-where-exists-select#details