Figuer:
CUSTOMER In Table CUSTOMER, CID Is the Primary Key (Customer ID)

Figuer:
CUSTOMER $$\begin{array} { | l | l | l | l | l | } \hline \text { CID } & \text { CNAME } & \text { AGE } & \text { RESID\_CITY } & \text { BIRTHPLACE } \\\hline 10 & \text { BLACK } & 40 & \text { ERIE } & \text { TAMPA } \\\hline 20 & \text { GREEN } & 25 & \text { CARY } & \text { ERIE } \\\hline 30 & \text { JONES } & 30 & \text { HEMET } & \text { TAMPA } \\\hline 40 & \text { MARTIN } & 35 & \text { HEMET } & \text { TAMPA } \\\hline 50 & \text { SIMON } & 22 & \text { ERIE } & \text { ERIE } \\\hline 60 & \text { VERNON } & 60 & \text { CARY } & \text { CARY } \\\hline\end{array}$$ In table CUSTOMER, CID is the primary key (Customer ID) .
RENTALS $$\begin{array} { | l | l | l | l | l | l | } \hline \text { CID } & \text { MAKE } & \text { DATE\_OUT } & \text { PICKUP } & \text { RETURN } & \text { RTN } \\\hline 10 & \text { FORD } & 10 - 0 c t - 1994 & \text { CARY } & \text { CARY } & 1 \\\hline 10 & \text { GM } & 01 - N o v - 1995 & \text { TAMPA } & \text { CARY } & 2 \\\hline 10 & \text { FORD } & 01 - J a n - 1995 & \text { ERIE } & \text { ERIE } & 3 \\\hline 20 & \text { NISSAN } & 07 - J u 1 - 1994 & \text { TAMPA } & \text { TAMPA } & 4 \\\hline 30 & \text { FORD } & 01 - J u l - 1995 & \text { CARY } & \text { ERIE } & 5 \\\hline 30 & \text { GM } & 01 - A u g - 1995 & \text { ERIE } & \text { ERIE } & 6 \\\hline 40 & \text { FORD } & 01 - A u g - 1994 & \text { CARY } & \text { ERIE } & 7 \\\hline 50 & \text { GM } & 01 - S e p - 19 95 & \text { ERIE } & \text { CARY } & 8 \\\hline 70 & \text { TOYOTA } & 02 - S e p - 1995 & \text { RENO } & \text { RENO } & 9 \\\hline\end{array}$$ In the table RENTALS, RTN provides the rental number (the primary key) , CID is the customer's unique id, PICKUP is the city where the car was picked up, and Return is the city where the car was returned.
RENTCOST $$\begin{array} { | l | l | } \hline \text { MAKE } & \text { COST } \\\hline \text { FORD } & 30 \\\hline \text { GM } & 40 \\\hline \text { NISSAN } & 30 \\\hline \text { TOYOTA } & 20 \\\hline \text { VOLVO } & 50 \\\hline\end{array}$$ RENTCOST shows the base cost of renting a given MAKE for one day.
CITYADJ $$\begin{array} { | l | l | } \hline \text { CITY } & \text { FACTOR } \\\hline \text { CARY } & 1 \\\hline \text { ERIE } & 1.1 \\\hline \text { RENO } & 0.9 \\\hline \text { TAMPA } & 0.8 \\\hline\end{array}$$ If the return city of table RENTALS is the one listed in table CITYADJ, the cost of the rental is multiplied by FACTOR and by DAYS shown in table RENTLENGTH below.
RENTLENGTH $$\begin{array} { | l | l | } \hline \text { RTN } & \text { DAYS } \\\hline 1 & 1 \\\hline 2 & 3 \\\hline 3 & 2 \\\hline 4 & 2 \\\hline 5 & 4 \\\hline 6 & 2 \\\hline 7 & 3 \\\hline 8 & 1 \\\hline\end{array}$$ RENTLENGTH shows the number of days for the rental number (RTN) shown in table RENTALS. In a database used in reality, this table would be merged with the RENTALS table.
-SELECT DISTINCT CNAME,AGE FROM CUSTOMER WHERE CID NOT IN
(SELECT CID FROM RENTALS)
This query is NOT equivalent (order ignored) to the following query:

A) SELECT DISTINCT CNAME, AGE FROM CUSTOMER, RENTALS WHERE CUSTOMER.CID <> RENTALS.CID
B) SELECT DISTINCT CNAME, AGE FROM CUSTOMER WHERE 0 IN (SELECT COUNT(*) FROM RENTALS
C) SELECT DISTINCT CNAME, AGE FROM CUSTOMER WHERE 0 = (SELECT COUNT(*) FROM RENTALS
WHERE CUSTOMER.CID = RENTALS.CID)
D) SELECT DISTINCT CNAME, AGE FROM CUSTOMER WHERE NOT EXISTS (SELECT CID FROM RENTALS