Exercise 6.3.6: We have noticed that certain operators of SQL are redun- dant, in the sense that they always can be replaced by other operators. For example, we saw that s IN R can be replaced by 8 = ANY R. Show that EXISTS and NOT EXISTS are redundant by explaining how to replace any expression of the form EXISTS R or NOT EXISTS R by an expression that does not involve EXISTS (except perhaps in the expression R itself). Hint: Remember that it is permissible to have a constant in the SELECT clause. Exercise 6.3.7: For these relations from our running movie database schema StarsIn(movieTitle, movieYear, starName) MovieStar(name, address, gender, birthdate) MovieExec(name, address, cert#, netWorth) Studio(name, address, presC#) describe the tuples that would appear in the following SQL expressions: a) Studio CROSS JOIN MovieExec; b) Stars In NATURAL FULL OUTER JOIN MovieStar; c) Stars In FULL OUTER JOIN MovieStar ON name = starName