Podcast
Questions and Answers
What is the correct relationship between database schema and instance?
Which attribute is most suitable to be a primary key for student data?
Which statement correctly describes the role of a foreign key?
What type of SQL statement is CREATE TABLE
?
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Which of the following queries can be used to replace a join operation accurately?
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What would the output be for the SQL query SELECT * FROM employee WHERE salary>10000 AND dept_id=101
?
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Which SQL statement contains a syntax error?
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In the SQL statement LIKE '_____ Computer Engineering'
, what character fits in the blank?
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What result does the query display after execution: (SELECT emp_id FROM employee WHERE dept = 'Toys') EXCEPT (SELECT emp_id FROM employee WHERE dept = 'Cars')?
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What placeholder is used in an aggregate expression to eliminate duplicates in the query SELECT COUNT (____ ID)?
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What should be used to represent missing phone numbers in a relation?
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Which statement correctly describes the requirement for a primary key attribute?
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What type of join allows for inclusion of rows that do not have matching values?
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Which command is used to delete all entries in a relation but retain its structure?
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Which statement correctly describes how to insert a tuple from another relation?
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What syntax is correct for declaring a view named 'v'?
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Study Notes
Multiple Choice Questions
- Q1: Database instance is a snapshot of current data, while schema designs the logical structure.
- Q2: Student ID is most likely the primary key for a student data table.
- Q3: An attribute can be a foreign key if it references a primary key in another relation.
-
Q4:
CREATE TABLE student (name VARCHAR, id INTEGER)
is a Data Definition Language (DDL) statement. -
Q5:
SELECT name, course_id FROM instructor, teaches WHERE instructor_ID = teaches_ID;
can be replaced bySELECT name, course_id FROM instructor NATURAL INNER JOIN teaches;
-
Q6: All columns (id, name, salary, dept_id) are displayed if
SELECT * FROM employee WHERE salary>10000 AND dept_id=101;
is executed. -
Q7:
Select id where id = 119 and name = 'Jane';
is the only statement with possible error. -
Q8:
%Computer Engineering
should be inserted into the blank to select the department with "Computer Engineering" as the ending string. -
Q9:
SELECT name FROM instructor WHERE salary BETWEEN 90000 AND 100000;
can replace the query to select instructor's names from a salary range. - Q10: Union operation automatically eliminates duplicated tuples and adds other tuples.
-
Q11: The query
(SELECT emp_id FROM employee WHERE dept = 'Toys') EXCEPT (SELECT emp_id FROM employee WHERE dept = 'Cars')
retrieves employee IDs from the Toys department that are not present in the Cars department. - Q12: Missing phone numbers in a relation are represented as NULL values.
- Q13: A primary key is both unique and not null.
-
Q14: To eliminate duplicates when counting, use the
DISTINCT
keyword. -
Q15: The SQL expression for "greater than at least one" is
> some
. -
Q16:
DELETE FROM instructor;
deletes all rows from the instructor table, preserving the table structure. -
Q17: SQL
INSERT
statements can copy data from other tables. - Q18: Outer joins include rows even if there's no match in the other table.
-
Q19: Use
CREATE VIEW v AS "query expression";
; to create viewv
. -
Q20: Integrity constraints like
CHECK(budget >= 0)
ensure non-negative budget values. -
Q21:
CREATE TABLE course...FOREIGN KEY (dept_name) REFERENCES department...
is a relational database design, defining a foreign key constraint that ensures data consistency between thecourse
anddepartment
tables. -
Q22: The
DROP TABLE
command is used to remove a table from a database. - Q23: To enforce a column to hold a value, Not null constraint should be applied.
-
Q24:
CREATE VIEW v AS "query expression";
defines a view in SQL. -
Q25:
ON DELETE CASCADE
specifies that deletion of a tuple in the parent table automatically deletes the related tuples in the child table. - Q26: Set difference ( - ) is the correct operator that gives the distinct.
-
Q27:
π C, D (S) ∩ π A, B (R)
returns the intersection of theC
andD
columns fromS
, and theA
andB
columns fromR
. -
Q28:
π B (S) - π B (R)
finds the values in column B of table S that are not also in column B of table R. -
Q29: SQL's
SELECT
clause corresponds to the relational algebra operationσ
. (selection) -
Q30: SQL query
SELECT a,b FROM r NATURAL INNER JOIN s WHERE r.A=2
matches relational algebra expressionσr.A=2(rxs)
. -
Q31:
Πbranch_name (σ branch_city = "London"(branch))
is used to retrieve branch names located in London. -
Q32:
Π customer_name (σ amount > 500(loan x customer))
is used to retrieve names of customers who have a loan amount larger than 500. -
Q33:
P (σcustomer_city="Paris"(customer))
finds customers residing in Paris, and returns the street and count along with customer name. -
Q34:
Π customer_name( σ depositor.customer_name = borrower.customer_name(R))
retrieves customer names having both a loan and an account. -
Q35:
Πbranch_name σ max (balance)(account))
is the query used to identify the branch name where the largest balance value is located. -
Q36: To increment loan amounts by 20%
Π loan_number, branch_name, amount* 1.2(loan)
is used. -
Q37:
R - σ branch_name = "Palm Springs”(S)
is used to delete accounts from a branch named Palm Springs. - Q38: The question is about composite primary keys. Customers can have multiple accounts, an account can be shared among multiple customers, and accounts can be present in several branch locations.
- Q39: Foreign key definitions involve referencing another table's primary key to maintain data integrity.
-
Q40:
SELECT staff_no, salary FROM Staff WHERE salary BETWEEN 100 AND 200 ORDER BY salary DESC
retrieves staff numbers and salaries within the 100-200 range in descending order. (inclusive). -
Q41:
SELECT count(distinct car_no) FROM rented WHERE rentDate BETWEEN '1-Jan-2021' AND '31-Jan-2021'
counts distinct cars rented in Jan 2021. -
Q42:
SELECT compNo, count(staff_no), SUM(salary) FROM Staff GROUP BY compNo HAVING count(staff_no) > 15;
finds companies with more than 15 staff and their total salary. -
Q43:
SELECT custNo, fName, IName FROM customer LEFT OUTER JOIN rented ON customer.custNo = rented.custNo
finds all customers with associated rental information or displays customers without any rentals. -
Q44:
SELECT playername FROM player WHERE playerid NOT IN (SELECT playerid FROM player_record)
is used to find all players who haven't played in any match. -
Q45:
SELECT refname, ref_age FROM referee WHERE league = 'Premier League' ORDER BY ref_age
finds the youngest referees in the Premier League. -
Q46:
UPDATE stock SET quantity = quantity - 100 WHERE code = 'A1'
decrements the quantity of items with code 'A1' by 100 units in the stock table. -
Q47:
DELETE FROM stock WHERE code = 'A1'
removes all rows with code 'A1' from the stock table.
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Description
Test your knowledge on database management concepts with this multiple-choice quiz. Topics include database instances, primary and foreign keys, and SQL statements. Perfect for students studying Database Systems.