DBMS and SQL MCQs for placement tests

Which SQL command removes all rows from a table but keeps the table structure?

Which normal form removes partial dependencies?

Which normal form removes transitive dependencies?

What does the 'A' in ACID stand for?

Which key uniquely identifies each row in a table and cannot be NULL?

A foreign key is used to:

What does this query return?

CREATE TABLE emp(name TEXT, salary INT);
INSERT INTO emp VALUES ('Asha', 50000), ('Ravi', 45000), ('Meena', 30000);
SELECT COUNT(*) FROM emp WHERE salary > 40000;

What does this query return?

CREATE TABLE emp(name TEXT, dept TEXT);
INSERT INTO emp VALUES ('A','IT'), ('B','IT'), ('C','HR');
SELECT dept, COUNT(*) FROM emp GROUP BY dept HAVING COUNT(*) > 1;

Which clause filters groups after GROUP BY?

Which join returns all rows from the left table and matching rows from the right table?

What does this query return?

CREATE TABLE emp(name TEXT, salary INT);
INSERT INTO emp VALUES ('Asha', 50000), ('Ravi', 45000), ('Meena', 30000);
SELECT MAX(salary) FROM emp WHERE salary < (SELECT MAX(salary) FROM emp);

Which SQL keyword removes duplicate rows from a result?

Which of these is a DDL (Data Definition Language) command?

Which of these is a DML (Data Manipulation Language) command?

What does COMMIT do in a transaction?

In an ER diagram, a relationship where one row of A relates to many rows of B is:

What does this query return?

CREATE TABLE c(id INT, name TEXT);
CREATE TABLE o(oid INT, cid INT);
INSERT INTO c VALUES (1,'A'), (2,'B');
INSERT INTO o VALUES (1,1), (2,1), (3,2);
SELECT COUNT(*) FROM c JOIN o ON c.id = o.cid;

Which aggregate function ignores NULL values?

An index on a column mainly helps to:

Which property ensures that once a transaction commits, its changes survive a crash?