Structured Query Language · Database Management System · GATE CSE

Consider a relational database containing the following schemas.
The primary key of each table is indicated by underlying the constituent fields.

SELECT s.sno, s.sname

FROM Suppliers s, Catalogue c

WHERE s.sno = c.sno AND

      Cost > (SELECT AVG (cost)

                 FROM Catalogue

                 WHERE pno = ‘P4’

                 GROUP BY pno);

The number of rows returned by the above SQL query is

Consider the following two tables and four queries in SQL.

Book (isbn, bname), Stock (isbn, copies)

Query 1:

SELECT B.isbn, S.copies
 FROM Book B INNER JOIN Stock S
 ON B.isbn = S.isbn;

Query 2:

SELECT B.isbn, S.copies
 FROM Book B LEFT OUTER JOIN Stock S
 ON B.isbn = S.isbn;

Query 3:

SELECT B.isbn, S.copies
 FROM Book B RIGHT OUTER JOIN Stock S
 ON B.isbn = S.isbn;

Query 4:

SELECT B.isbn, S.copies
 FROM Book B FULL OUTER JOIN Stock S
 ON B.isbn = S.isbn;

Which one of the queries above is certain to have an output that is a superset of the outputs of the other three queries?

SELECT operation in SQL is equivalent to

Consider the following relation
$$\,\,\,\,\,\,\,\,$$ Cinema(theater, address, capacity)
Which of the following options will be needed at the end of the $$SQL$$ query

$$\,\,\,\,\,\,\,\,$$ SELECT $$P1.$$address
$$\,\,\,\,\,\,\,\,$$ FROM Cinema $$P1$$

such that it always finds the addresses of theaters with maximum capacity?

Given the following statements:

S1: A foreign key declaration can always be replaced by an equivalent check assertion in SQL.

S2: Given the table R(a,b,c) where a and b together form the primary key, the following is a valid table definition.

CREATE TABLE S (
 a INTEGER,
 d INTEGER,
 e INTEGER,
 PRIMARY KEY (d),
 FOREIGN KEY (a) references R)

Which one of the following statements is CORRECT?

Which of the following statements are TRUE about an SQL query?

P: An SQL query can contain a HAVING clause even if it does not have a GROUP BY clause
Q: An SQL query can contain a HAVING clause only if it has a GROUP BY clause
R: All attributes used in the GROUP BY clause must appear in the SELECT clause
S: Not all attributes used in the GROUP BY clause need to appear in the SELECT clause

A relational schema for a train reservation database is given below:

Passenger ( pid, pname, age)
Reservation (pid, cass, tid)

Table: Passenger

pid	pname	age
0	'Sachin'	65
1	'Rahul'	66
2	'Sourav'	67
3	'Anil'	69

Table: Reservation

pid	class	tid
0	'AC'	8200
1	'AC'	8201
2	'SC'	8201
5	'AC'	8203
1	'SC'	8204
3	'AC'	8202

What pids are returned by the following SQL query for the above instance of the tables?

SELECT   pid
FROM   Reservation
WHERE   class 'AC' AND 
EXISTS (SELECT * 
FROM Passenger 
WHERE age > 65 
AND Passenger.pid = Reservation.pid);

Consider the following relation schema pertaining to a students database:

Students (rollno, name, address)
Enroll(rollno,courseno, coursename)

Where the primary keys are shown underlined. The number of tuples in the student and Enroll tables are 120 and 8 respectively. What are the maximum and minimum number of tuples that can be present in (Student * Enroll), where '*' denotes natural join?

Consider the following table named Student in a relational database. The primary key of this table is rollNum.

Student

rollNum	name	gender	marks
1	Naman	M	62
2	Aliya	F	70
3	Aliya	F	80
4	James	M	82
5	Swati	F	65

The SQL query below is executed on this database.

SELECT *

FROM Student

WHERE gender = 'F' AND

marks > 65;

The number of rows returned by the query is _____________.

Consider the relational database with the following four schemas and their respective instances.

Student( $$\underline {sNo} $$ , sName, dNo) Dept( $$\underline {dNo} $$ , dName)

Course( $$\underline {cNo} $$ , cName, dNo) Register( $$\underline {sNo} $$ , $$\underline {cNo} $$ )

SQL Query :

SELECT * FROM Student AS S WHERE NOT EXIST

(SELECT cNo FROM Course WHERE dNo = "D01"

EXCEPT

SELECT cNo FROM Register WHERE sNo = S.sNo)

The number of rows returned by the above SQL query is _____________.

The relation scheme given below is used to store information about the employees of a company, where empId is the key and deptId indicates the department to which the employee is assigned. Each employee is assigned to exactly one department.

emp(empId, name, gender, salary, deptId)

Consider the following SQL query:

select deptId, count(⋆)

from emp

where gender = "female" and salary > (select avg(salary) from emp)

group by deptId;

The above query gives, for each department in the company, the number of female employees whose salary is greater than the average salary of

A relational database contains two tables Student and Performance as shown below :

The primary key of the Student table is Roll_no. For the Performance table, the columns Roll_no. and Subject_code together from the primary key. Consider the SQL query given below:

SELECT S.Student_name, sum (P.Marks)
       FROM Student S, Performance P
       WHERE P.Marks > 84
       GROUP BY S.Student_name;

The number of rows returned by the above SQL query is _________.

Consider the following database table named $$water$$_$$schemes :$$

	water_schemes
scheme_no	district_name	capacity
1	Ajmer	20
1	Bikaner	10
2	Bikaner	10
3	Bikaner	20
1	Churu	10
2	Churu	20
1	Dungargarh	10

The number of tuples returned by the following $$SQL$$ query is _______________.

with total(name, capacity) as
    select district_name, sum(capacity)
    from water_schemes
    group by district_name
with total_avg(capacity) as
    select avg(capacity)
    from total
select name
    from total, total_avg
    where total.capacity ≥ total_avg.capacity

Consider the following relation:

Student

Roll_No	Student_Name
1	Raj
2	Rohit
3	Raj

Performance

Roll_No	Course	Marks
1	Math	80
1	English	70
2	Math	75
3	English	80
2	Physics	65
3	Math	80

Consider the following SQL query.

SELECT S.Student_Name, Sum(P.Marks) 
FROM Student S, Performance P
WHERE S.Roll_No= P.Roll_No
GROUP BY S.STUDENT_Name

The numbers of rows that will be returned by the SQL query is___________.

SQL allows duplicate tuples in relations, and correspondingly defines the multiplicity of tuples in the result of joins. Which one of the following queries always gives the same answer as the nested query shown below:

Select * from R where a in (select S.a from S)

Consider the following relational schema:

employee (empId, empName, empDept )

customer (custId, custName, salesRepId, rating)

SalesRepId is a foreign key referring to empId of the employee relation. Assume that each employee makes a sale to at least one customer. What does the following query return?

SELECT empName 
FROM employee E 
WHERE NOT EXISTS (SELECT custId 
       FROM customer C 
       WHERE C.salesRepId = E.empId 
       AND C.rating <> 'GOOD');

Given the following schema:

employees(emp-id, first-name, last-name, hire-date, dept-id, salary)

departments(dept-id, dept-name, manager-id, location-id)

You want to display the last names and hire dates of all latest hires in their respective departments in the location ID 1700. You issue the following query:

SQL> SELECT last-name, hire-date 
FROM employees WHERE (dept-id, hire-date) IN 
(SELECT dept-id, MAX(hire-date) 
FROM employees JOIN departments USING(dept-id) 
WHERE location-id = 1700
GROUP BY dept-id);

What is the outcome?

Consider the following relational schema.

Students(rollno: integer, sname: string)

Courses(courseno: integer, cname: string)

Registration(rollno: integer, courseno: integer, percent: real)

Which of the following queries are equivalent to this query in English?

"Find the distinct names of all students who score more than 90% in the course numbered 107"

(I) SELECT DISTINCT S.sname 
FROM Students as S, Registration as R 
WHERE R.rollno=S.rollno AND 
R.courseno=107 AND R.percent >90

(II) ∏_sname(σ_courseno = 107 ∧ percent > 90 (Registration ⋈ Students))

(III) { T | ∃S ∈ Students, ∃R ∈ Registration ( S.rollno=R.rollno ∧ R.courseno=107 ∧ R.percent > 90 ∧ T.sname=S.sname)}

(iv) { < S_N >| ∃S_R∃R_P ( < S_R, S_N > ∈ Students ∧ ∈ Registration ∧ R_P > 90)}

Database table by name Loan_Records is given below.

Borrower	Bank_Manager	Loan_Amount
Ramesh	Sunderajan	10000.00
Suresh	Ramgopal	5000.00
Mahesh	Sunderajan	7000.00

What is the output of the following SQL query?

SELECT count(*) 
FROM ( 
(SELECT Borrower. Bank_Manager FROM Loan_Records) AS S 
NATURAL JOIN 
(SELECT Bank_Manager, Loan_Amount FROM Loan_Records) AS T );

Consider a database table T containing two columns X and Y each of type integer. After the creation of the table, one record (X = 1, Y = 1) is inserted in the table.

Let MX and MY denote the respective maximum values of X and Y among all records in the table at any point in time. Using MX and MY, new records are inserted in the table 128 times with X and Y values being MX + 1, 2*MY + 1 respectively. It may be noted that each time after the insertion, values of MX and MY change.

What will be the output of the following SQL query after the steps mentioned above are carried out?

SELECT Y FROM T WHERE X=7; 

Consider the following relational schema:

Suppliers(sid : integer, sname : string, city : string, street : string)

Parts(pid : integer, pname : string, color : string)

Catalog(sid : integer, pid : integer, cost : real)

Consider the following relational query on the above database:

SELECT S.sname 
FROM Suppliers S 
WHERE S.sid NOT IN 
     (SELECT C.sid 
      FROM Catalog C 
      WHERE C.pid NOT IN 
        (SELECT P.pid 
         FROM Parts P 
         WHERE P.color<> 'blue'))

Assume that relations corresponding to the above schema are not empty. Which one of the following is the correct interpretation of the above query?

Consider the following relational schema:

Suppliers(sid : integer, sname : string, city : string, street : string)

Parts(pid : integer, pname : string, color : string)

Catalog(sid : integer, pid : integer, cost : real)

Assume that, in the suppliers relation above, each supplier and each street within a city has a unique name, and (sname, city) forms a candidate key. No other functional dependencies are implied other than those implied by primary and candidate keys. Which one of the following is TRUE about the above schema?

Consider The Following Relational Scheme

Student (school-id, sch-roll-no, sname, saddress)
School (school-id, sch-name, sch-address, sch-phone)
Enrolment (school-id, sch-roll-no, erollno, examname)
ExamResult (Erollno, examname, marks)

Consider the following tuple relational calculus query

{ t | ∃E ∈ Enrolment t = E.school-id ∧ 
| { x | x ∈ ExamResult B.school-id = 
t ∧ ( ∃B ∈ ExamResult B.erollno = 
x.erollno ∧ B.examname = x.examname ∧ 
B.marks > 35 } | ÷ | 
{ x | x ∈ Enrolment ∧ x.school-id = t } 
| * 100 > 35 }

If a student needs to score more than 35 marks to pass an exam what does the query return?

Consider The Following Relational Scheme

Student (school-id, sch-roll-no, sname, saddress)
School (school-id, sch-name, sch-address, sch-phone)
Enrolment (school-id, sch-roll-no, erollno, examname)
ExamResult (Erollno, examname, marks)

What does the following SQL query output?

SELECT sch-name, COUNT (*) 
FROM School C, Enrolment E, 
ExamResult R 
WHERE E.school-id = C.school-id 
AND E.examname = R.examname 
AND E.erollno = R.erollno
AND R.marks = 100 AND S.school-id IN 
(SELECT school-id 
 FROM student 
 GROUP BY school-id 
 HAVING COUNT (*) > 200) 
GROUP BY school-id;

Consider the table employee(empId, name, department, salary) and the two queries Q₁, Q₂ below. Assuming that department 5 has more than one employee, and we want to find the employees who get higher salary than anyone in the department 5, which one of the statements is TRUE for any arbitrary employee table?

Q1:
Select e.empId 
From employee e 
Where not exists 
  (Select * From employee s
   where s.department = "5" and 
   s.salary >=e.salary);

Q2:
Select e.empId 
From employee e 
Where e.salary > Any 
( Select distinct salary 
From employee s 
Where s.department = "5");

Consider the relation account (customer, balance) where customer is a primary key and there are no null values. We would like to rank customers according to decreasing balance. The customer with the largest balance gets rank 1. Ties are not broke but ranks are skipped: if exactly two customers have the largest balance they each get rank 1 and rank 2 is not assigned.

Query1:
  Select A.customer, count(B.customer)
  From account A, account B
  Where A.balance <=B.balance
  Group by A.customer

Query2:
  Select A.customer, 1+count(B.customer)
  From account A, account B
  Where A.balance < B.balance
  Group by A.customer

Consider these statements about Query1 and Query2.

1. Query1 will produce the same row set as Query2 for some but not all databases.

2. Both Query1 and Query2 are correct implementation of the specification

3. Query1 is a correct implementation of the specification but Query2 is not

4. Neither Query1 nor Query2 is a correct implementation of the specification

5. Assigning rank with a pure relational query takes less time than scanning in decreasing balance order assigning ranks using ODBC.

Which two of the above statements are correct?

Consider the relation "enrolled (student, course)" in which (student, course) is the primary key, and the relation "paid (student, amount)" where student is the primary key. Assume no null values and no foreign keys or integrity constraints. Given the following four queries:

Query 1:

Select student 
from enrolled 
where student in (select student from paid)

Query 2:

Select student 
from paid 
where student in (select student from enrolled)

Query 3:

Select E.student 
from enrolled E, paid P 
where E.student = P.student

Query 4:

Select student 
from paid 
where exists (Select * 
              from enrolled 
              where enrolled.student = paid.student)

Which one of the following statements is correct?

Consider a database with three relation instances shown below. The primary keys for the Drivers and Cars relation are Did and cid respectively and the records are stored in ascending order of these primary keys as given in the tables. No indexing is available in the database.

D: Drivers Relation

Did	Dname	rating	Age
22	Karthikeyan	7	25
29	Salman	1	33
31	Boris	8	55
32	Amoldt	8	25
58	Schumacher	10	35
64	Sachin	7	35
71	Senna	10	16
74	Sachin	9	35
85	Rahul	3	25
95	Ralph	3	53

R: Reserves Relation

Did	cid	Day
22	101	10/10/06
22	102	10/10/06
22	103	8/10/06
22	104	7/10/06
31	102	10/11/06
31	103	6/11/06
31	104	12/11/06
64	101	5/9/06
64	102	8/9/06
74	103	8/9/06

C: Cars relation

cid	Cname	Color
101	Renault	Blue
102	Renault	Red
103	Ferrari	Green
104	Jaguar	Red

Select D.dname 
From Drivers D 
Where D.did in (SELECT R.did 
                From Cars C,Reserves R 
                WHERE R.cid = C.cid and C.color = 'green')

Let n be the number of comparisons performed when the above SQL query is optimally executed. If linear search is used to locate a tuple in a relation using primary key, then n lies in the range

Consider a database with three relation instances shown below. The primary keys for the Drivers and Cars relation are Did and cid respectively and the records are stored in ascending order of these primary keys as given in the tables. No indexing is available in the database.

D: Drivers Relation

Did	Dname	rating	Age
22	Karthikeyan	7	25
29	Salman	1	33
31	Boris	8	55
32	Amoldt	8	25
58	Schumacher	10	35
64	Sachin	7	35
71	Senna	10	16
74	Sachin	9	35
85	Rahul	3	25
95	Ralph	3	53

R: Reserves Relation

Did	cid	Day
22	101	10/10/06
22	102	10/10/06
22	103	8/10/06
22	104	7/10/06
31	102	10/11/06
31	103	6/11/06
31	104	12/11/06
64	101	5/9/06
64	102	8/9/06
74	103	8/9/06

C: Cars relation

cid	Cname	Color
101	Renault	Blue
102	Renault	Red
103	Ferrari	Green
104	Jaguar	Red

What is the output of the following SQL query?

Select D.dname 
From Drivers D 
Where D.did in (SELECT R.did 
                From Cars C,Reserves R 
                WHERE R.cid = C.cid and C.color = 'green')

The relation book (title, price) contains the titles and prices of different books. Assuming that no two books have the same price, what does the following SQL query list?

Select title
 From book as B
 Where (select count(*)
   From book as T
   Where T.price > B.price) < 5;

A company maintains records of sales made by its salespersons and pays them commission based on each individual’s total sales made in a year. This data is maintained in a table with following schema:

salesinfo = (salespersonid, totalsales, commission)

In a certain year, due to better business results, the company decides to further reward its salespersons by enhancing the commission paid to them as per the following formula:

If commission < = 50000, enhance it by 2%
If 50000 < commission < = 100000, enhance it by 4%
If commission > 100000, enhance it by 6%

The IT staff has written three different SQL scripts to calculate enhancement for each slab, each of these scripts is to run as a separate transaction as follows:

T1: Update salesinfo
 Set commission = commission * 1.02
 Where commission < = 50000;

T2: Update salesinfo
 Set commission = commission * 1.04
 Where commission > 50000 and commission is < = 100000;

T3: Update salesinfo
 Set commission = commission * 1.06
 Where commission > 100000;

Which of the following options of running these transactions will update the commission of all salespersons correctly?

In an inventory management system implemented at a trading corporation, there are several tables designed to hold all the information. Amongst these, the following two tables hold information on which items are supplied by which suppliers, and which warehouse keeps which items along with the stock-level of these items.

Supply = (supplierid, itemcode)
Inventory = (itemcode, warehouse, stocklevel)

For a specific information required by the management, following SQL query has been written

Select distinct STMP.supplierid 
From Supply as STMP 
Where not unique (Select ITMP.supplierid 
    From Inventory, Supply as ITMP 
    Where STMP.supplierid = ITMP.supplierid 
    And ITMP.itemcode = Inventory.itemcode 
    And Inventory.warehouse = 'Nagpur');

For the warehouse at Nagpur, this query will find all suppliers who

Consider two tables in a relational database with columns and rows as follows:

 Table: Student

Roll_no	Name	Dept_id
1	ABC	1
2	DEF	1
3	GHI	2
4	JKL	3

 Table: Department

Dept_id	Dept_name
1	A
2	B
3	C

Roll_no is the primary key of the Student table, Dept_id is the primary key of the Department table and Studetn.Dept_id is a foreign key from
Department. Dept_id.

What will happen if we try to execute the following two SQL statements?

(i) update Student set Dept_id = Null where Roll_no =1
(ii) update Department set Dept_id = Null where Dept_id =1

A relational database contains two table student and department in which student table has columns roll_no, name and dept_id and department table has columns dept_id and detp_name. the following insert statements were executed successfully to populate the empty tables:

 Insert into department values (1, ‘Mathematics’)
 Insert into department values (2, ‘Physics’)
 Insert into student values (1, ‘Navin’,1)
 Insert into student values (2, ‘Mukesh’,2)
 Insert into student values (3, ‘Gita’,1)

How many rows and columns will be retrieved by the following SQL statement?

Select * from student, department;

The employee information in a company is stored in the relation

Employee (name, sex, salary, deptName)

Consider the following SQL query

  Select deptName
  From Employee
  Where sex = ‘M’
  Group by deptName
  Having avg(salary) >
  (Select avg (salary) From Employee);

It returns the names of the department in which

Consider the set of relations shown below and the SQL query that follows.

Students: (Roll_number, Name, Date_of_birth)
Courses: (Course number, Course_name, Instructor)
Grades: (Roll_number, Course_number, Grade)

Select distinct Name
From Students, Courses, Grades
Where Students.Roll_number = Grades.Roll_number
      and Courses.Instructor = 'Korth'
      and Courses.Course_number = Grades.Course_number
      and Grades.grade = 'A';

Which of the following sets is computed by the above query?

In SQL, relations can contain null values, and comparisons with null values are treated as unknown. Suppose all comparisons with a null value are treated as false. Which of the following pairs is not equivalent?

Given relations r( w, x ) and s( y, z ), the result of

select distinct w,x
from r, s;

is guaranteed to be same as r, provided

Which of the following is/are correct?

Consider the set of relations

EMP (Employee-no, Dept-no, Employee-name, Salary)
DEPT (Dept-no, Dept-name, Location)

Write an SQL query to:

(a) Find all employee names who work in departments located at "Calcutta" and whose salary is greater than Rs.50,000.

(b) Calculate, for each department number, the number of employees with a salary greater than Rs.1,00,000.

Suppose we have a database consisting of the following three relations.

FREQUENTS (student, parlor) giving the parlors each student visits.

SERVES (parlor, ice-cream) indicating what kind of ice-creams each parlor serves.

LIKES (student, ice-cream) indicating what ice-creams each student likes.

(Assume that each student likes at least one ice-cream and frequents at least one parlor)

Express the following in SQL:
Print the students that frequent at least one parlor that serves some ice-cream that they like.