Question $4.$

$[6$ MARKS$]$

Consider the following schema. Primary keys are underlined.

The following syntactically correct queries in SQL and relational algebra attempt to return the set $($i$.$e$.,$

with no duplicates$)$ of all SIDs of all Sailors who have never reserved a red boat. For each, circle one

answer to indicate whether it is correct or incorrect. Note that the symbol means "not equal to$"$ or $.$

select S$.$SID

from Sailor $S$

where S$.$SID not in $($ select R$.$SID

from Reserve R$,$ Boat B

where B$.$Color $=$ 'red'$)$

Circle one: correct incorrect

select distinct S$.$SID

from Sailor S$,$ Reserve R$,$ Boat B

where S$.$SID $=$ R$.$SID and R$.$BID $=$ B$.$BID and B$.$Color 'red'

Circle one: correct incorrect

select S$.$SID

from Sailor $S$

where not exists $($ select R$.$SID

from Reserve R$,$ Boat B

where S$.$SID $=$ R$.$SID and R$.$BID $=$ B$.$BID and B$.$Color $=$ 'red' $)$

Circle one: correct incorrect

select distinct R$.$SID

from Reserve R$,$ Boat B

where $R.$BID$=B.$BID and B$.$color $=$ 'red'

group by R$.$SID

having count$(**)<mn>1</mn>$

Circle one: correct incorrect

Sailor