Consider the relation employee(name, sex, supervisorName) with name as the key, supervisorName gives the name of the supervisor of the employee under consideration. What does the following Tuple Relational Calculus query produce?
$$\eqalign{ & \{ e.name\,|\,employee(e) \wedge \cr & (\forall x)[\neg employee(x) \vee \cr & x.\sup ervisorName \ne e.name\, \vee \cr & x.sex = 'male']\} \cr} $$b-Schema = (b-name, b-city, assets)
a-Schema = (a-num, b-name, bal)
d-Schema = (c-name, a-number)
Let branch, account and depositor be respectively instances of the above schemas. Assume that account and depositor relations are much bigger than the branch relation.
Consider the following query:Пc-name (σb-city = “Agra” ⋀ bal < 0 (branch $$ \Join $$ (account $$ \Join $$ depositor))
Which one of the following queries is the most efficient version of the above query ?
Table: student
Roll | Name | Hostel | Marks |
---|---|---|---|
1798 | Manoj Rathod | 7 | 95 |
2154 | Soumic Banerjee | 5 | 68 |
2369 | Gumma Reddy | 7 | 86 |
2581 | Pradeep Pendse | 6 | 92 |
2643 | Suhas Kulkarni | 5 | 78 |
2711 | Nitin Kadam | 8 | 72 |
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:
$$\eqalign{ & S' = \prod\nolimits_{hostel} {(({\sigma _{S.roll = H.roll}}} \cr & ({\sigma _{marks > 75\,\,\,and\,\,roll > 2000\,\,and\,\,roll < 3000}}(S))X(H)) \cr} $$The difference between the number of rows output by the SQL statement and the number of tuples in S’ is