Which one is Quicker , Exists or Join ?

EXISTS : is used to return a Boolean value
JOIN : returns a whole other table

EXISTS is only used to test if a sub query returns results, and short circuits as soon as it does. JOIN is used to extend a result set by combining it with additional fields from another table to which there is a relation. SO EXISTS  is fast and  JOIN  is slow comparatively. Let see it with an example

SET STATISTICS IO ON
SET STATISTICS TIME ON

SELECT * FROM BOOKS WHERE EXISTS
(
    SELECT NewSeqCol FROM MYTABLE
)



SELECT * FROM BOOKS
JOIN MYTABLE ON BOOKS.id = MYTABLE.NewSeqCol



above are the result sets returned from both of the queries , as you can see from the elapsed time durations difference is clear.