Consider the relational schema of sailors $S$, Reserves $R$ and Boats $B$.Table 1: Sailors $S$

Sid	Sname	Rating	Age
22	Dustin	7	45.0
29	Brutus	1	33.0
31	Lubber	8	55.5
32	Andy	8	25.5
58	Rusty	10	35.5
64	Horatio	7	35.5
71	Zorba	10	16.0
74	Horatio	9	35.0
85	Art	3	25.5
95	Bob	3	63.5

Table 2: Reserves $R$

Sid	Bid	day
22	101	10/10/98
22	102	10/10/98
22	103	10/8/98
22	104	10/7/98
31	102	11/10/98
31	103	11/6/98
31	104	11/12/98
64	101	9/5/98
64	102	9/8/98
74	103	9/8/98

Table 3: Boats $B$

Bid	Bname	Color
101	Interlake	blue
102	Interlake	red
103	Clipper	green
104	Marine	red

Which of the following relational algebra query/queries computes/compute the names of sailors who have reserved a red boat?Q1 $\pi_{sname}((\sigma_{color='red'}(Boats))\bowtie Reserves\bowtie Sailors)$Q2 $\pi_{sname}((\pi_{sid}((\pi_{bid}(\sigma_{color='red'}(Boats)))\bowtie Reserves))\bowtie Sailors)$Q3 $\pi_{sname}((\sigma_{color='red'}(Reserves))\bowtie Boats\bowtie Sailors)$

We need the names of sailors who have reserved a red boat.

First, we must identify red boats from the Boats table.

Red boats are obtained by:

$\sigma_{color='red'}(Boats)$

After this, we need to join these red boats with Reserves table, because Reserves table tells which sailor reserved which boat.

Then we join with Sailors table to get sailor names.

So, Q1 is correct:

$\pi_{sname}((\sigma_{color='red'}(Boats))\bowtie Reserves\bowtie Sailors)$

Now check Q2.

Q2 first finds red boat IDs:

$\pi_{bid}(\sigma_{color='red'}(Boats))$

Then it joins with Reserves to find sailors who reserved those red boats.

Then it projects $sid$ and joins with Sailors to get sailor names.

So, Q2 is also correct.

Now check Q3.

Q3 applies condition $color='red'$ on Reserves.

But Reserves table does not contain the attribute $color$.

The $color$ attribute belongs to Boats table.

So, Q3 is incorrect.

Therefore, both Q1 and Q2 compute the required result.