Question $1$

Bob owns a computer store and sells computers. $$He has a database with a relation:

Sells $($computerName$,$ price$)$

Bob and Alice are performing queries on the Sells relation. $$Assume Each one of Bob's queries run in individual transactions. Assume ALL of Alice's queries run in a SINGLE transaction.

The initial state of the Sells relation is:

Sells$($ storeName $($str$),$ computerName $($str$),$ price $($float$))$

$($ 'Bob store', $$ 'econo computer', $100\mathrm{.}00)$

$($ 'Bob store', $$ 'nice computer', $300\mathrm{.}00)$

$$Bob will perform the following queries:

$($del$)$ DELETE from Sells WHERE storeName $=$ 'Bob store';

$($ins$)$ INSERT INTO Sells VALUES $(\text{'}$Bob store', 'super cpu', $800\mathrm{.}00)$;

Alice will perform the following queries:

$($min$)$ SELECT min$($ price $)$ FROM Sells WHERE storeName $=$ 'Bob store'

$($max$)$ SELECT max$($ price $)$ FROM Sells WHERE storeName $=$ 'Bob store'

What will the $($max$)$ query return for Alice for if queries arrive at the database in the following sequence if Alice is using SERIALIZABLE transaction level?

$($del$)($ins$)($min$)($max$)$

$100$

$300$

$800$

$1000$

$1$ points $$

Question $2$

Copy of

Bob owns a computer store and sells computers. $$He has a database with a relation:

Sells $($computerName$,$ price$)$

Bob and Alice are performing queries on the Sells relation. $$Assume Each one of Bob's queries run in individual transactions. Assume ALL of Alice's queries run in a SINGLE transaction.

The initial state of the Sells relation is:

Sells$($ storeName $($str$),$ computerName $($str$),$ price $($float$))$

$($ 'Bob store', $$ 'econo computer', $100\mathrm{.}00)$

$($ 'Bob store', $$ 'nice computer', $300\mathrm{.}00)$

$$Bob will perform the following queries:

$($del$)$ DELETE from Sells WHERE storeName $=$ 'Bob store';

$($ins$)$ INSERT INTO Sells VALUES $(\text{'}$Bob store', 'super cpu', $800\mathrm{.}00)$;

Alice will perform the following queries:

$($min$)$ SELECT min$($ price $)$ FROM Sells WHERE storeName $=$ 'Bob store'

$($max$)$ SELECT max$($ price $)$ FROM Sells WHERE storeName $=$ 'Bob store'

What will the $($max$)$ query return for Alice for if queries arrive at the database in the following sequence if Alice is using READ COMMITTED transaction level?

$($del$)($ins$)($min$)($max$)$

$100$

$300$

$800$

$1000$

$1$ points $$

Question $3$

Copy of

Copy of

Bob owns a computer store and sells computers. $$He has a database with a relation:

Sells $($computerName$,$ price$)$

Bob and Alice are performing queries on the Sells relation. $$Assume ALL of Bob's queries run in a SINGLE transaction. Assume ALL of Alice's queries run in a SINGLE transaction.

The initial state of the Sells relation is:

Sells$($ storeName $($str$),$ computerName $($str$),$ price $($float$))$

$($ 'Bob store', $$ 'econo computer', $100\mathrm{.}00)$

$($ 'Bob store', $$ 'nice computer', $300\mathrm{.}00)$

$$Bob will perform the following queries:

$($del$)$ DELETE from Sells WHERE storeName $=$ 'Bob store';

$($ins$)$ INSERT INTO Sells VALUES $(\text{'}$Bob store', 'super cpu', $800\mathrm{.}00)$;

Alice will perform the following queries:

$($min$)$ SELECT min$($ price $)$ FROM Sells WHERE storeName $=$ 'Bob store'

$($max$)$ SELECT max$($ price $)$ FROM Sells WHERE storeName $=$ 'Bob store'

What will the $($max$)$ query return for Alice for if queries arrive at the database in the following sequence if Alice is using READ UNCOMMITTED transaction level?

$($del$)($ins$)($min$)($max$)$