October 4, 2023
October 4, 2023
October 4, 2023
###### SQL
October 4, 2023
 Question 26

A table ‘student’ with schema (roll, name, hostel, marks), and another table ‘hobby’ with schema (roll, hobbyname) contains records as shown below:

```Table: Student
ROLL	    NAME	HOSTEL	MARKS
1798	Manoj Rathod	  7	 95
2154	Soumic Banerjee	  5	 68
2369	Gumma Reddy	  7	 86
2643	Suhas Kulkarni	  5	 78
2872	Kiran Vora	  5	 92
2926	Manoj Kunkalikar  5	 94
2959	Hemant Karkhanis  7	 88
3125	Rajesh Doshi	  5	 82

Table: hobby
ROLL	HOBBYNAME
1798	chess
1798	music
2154	music
2369	swimming
2581	cricket
2643	chess
2643	hockey
2711	volleyball
2872	football
2926	cricket
2959	photography
3125	music
3125	chess ```

The following SQL query is executed on the above tables:

```select hostel
from student natural join hobby
where marks >= 75 and roll between 2000 and 3000; ```

Relations S and H with the same schema as those of these two tables respectively contain the same information as tuples. A new relation S’ is obtained by the following relational algebra operation:

`S’ = ∏hostel ((σs.roll = H.roll(σmarks > 75 and roll > 2000 and roll < 3000 (S)) X (H))  `

The difference between the number of rows output by the SQL statement and the number of tuples in S’ is

 A 6 B 4 C 2 D 0
Question 26 Explanation:
SQL query will return:

Total 7 rows are selected.
Where in relational algebra only distinct values of hostels are selected,i.e., 5, 6, 7 (3 rows).
∴ Answer is 7 – 3 = 4
Question 26 Explanation:
SQL query will return:

Total 7 rows are selected.
Where in relational algebra only distinct values of hostels are selected,i.e., 5, 6, 7 (3 rows).
∴ Answer is 7 – 3 = 4
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