Hello. Please, help me with some queries. Thank you very much. 1.Using a subquer

Question

Hello. Please, help me with some queries. Thank you very much.

1.Using a subquery, list which service categories have never been assigned or worked on.
2.Using a subquery, which unit(s) does Alyssa Kelly own?
3.Whose condo fee is more than the average condo fee?
14.Using an EXISTS, which service categories have had more than 5 hours of work spent total?

SERVICE REQUEST SERVICE CATEGORY CATEGORY_NUM SERVICELID CONDO D CATEGORY NUM STATUS EST HOURS SPENT HOURS NEXT SERVICE DATE CONDO UNIT CONDOLD UNIT NUM SOR FT BDRMS BATHS CONDO FEE OWNER NUM OWNER OWNER NUM LAST NAME FIRST NAME ADDRESS CITY STATE POSTAL CODE LOCATION ADDRESS CITY STATE POSTAL CODE

Explanation / Answer

If you have any doubts, please give me comment...

-- 1)

SELECT CATEGORY_NUM, CATEGORY_DESCRIPTION

FROM SERVICE_CATEGORY

WHERE CATEGORY_NUM NOT IN(

SELECT CATEGORY_NUM

FROM SERVICE_REQUEST

);

-- 2)

SELECT UNIT_NUM

FROM CONDO_UNIT

WHERE OWNER_NUM IN(

SELECT OWNER_NUM

FROM OWNER

WHERE LAST_NAME = 'Alyssa' AND FIRST_NAME = 'Kelly'

);

-- 3)

SELECT CONDO_FEE

FROM CONDO_UNIT

WHERE CONDO_FEE > (

SELECT AVG(CONDO_FEE)

FROM CONDO_UNIT

);

-- 4)

SELECT CATEGORY_NUM, CATEGORY_DESCRIPTION

FROM SERVICE_CATEGORY SC

WHERE EXISTS(

SELECT *

FROM SERVICE_REQUEST SR

WHERE SC.CATEGORY_NUM = SR.CATEGORY_NUM AND SPENT_HOURS > 5

);

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