Exists query

Hi,

If anyone would know if below 2 queries are the same:

select * from test1 where exists (select 'X' from test2 where test1.col1=test2.col1);

select * from test1 where exists (select * from test2 where test1.col1=test2.col1);

The query different is with 'X' and * in the subquery? anyone know if both are the same? or any purpose why we are putting 'X' instead of * ?

Any input is greatly appreciated.

Thanks and best regards.