SQL and Database Concepts Quiz1

What does the following SQL statement do? Delete from Customer_T where state = ‘HI’;

• Deletes all records from customer_t where the state is equal to HI

• Removes the Customer_T table from the database

• Deletes all records from the Customer_T table

• Doesn’t delete anything because of a syntax error

Which of the following is one of the basic types of joins in DB?

• Outer join

• Self-join

• Equi-join

• All of the above

Which of the below SELECT statement is used to select all columns of EMP table?

• SELECT ALL FROM emp

• SELECT # FROM emp

• SELECT * FROM emp

• SELECT empno, ename, deptno, sal, job, mgr, hiredate FROM emp

Select DatePart(yy, ‘20/01/2021’) As ‘Năm’

• 01

• 2021

• 20

• 20/01/2021

Determine the error in the below SELECT statement SELECT ename, deptno, sal FROM emp WHERE job=CLERK;

• WHERE clause cannot refer the column JOB since it doesn’t appear in the SELECT column list

• Character literal CLERK must be enclosed within single quotes

• Character literal CLERK must be enclosed within parentheses

• No error in the query

What are the benefits of Triggers?

• Generating some derived column values automatically

• Enforcing referential integrity

• Synchronous replication of tables

• All of the above

Consider the following steps: Transaction A retrieves record R at time T Transaction B retrieves the same record at time T+1 Transaction A updates the record at time T+2 (based on value seen at time T) Transaction B updates the same record at time T+3 (based on value seen at time T+1) What is the result of the above sequence of steps?

• Transaction B’s update would be overwritten by transaction A’s update

• Transaction A’s update would be overwritten by transaction B’s update

• Transaction B’s update would be overwritten by transaction B’s update

• Transaction A’s update would be overwritten by transaction A’s update

A table TEST_COUNT has 10 number values as 3, 32, 1, 1, null, 24, 12, null, 32, null Predict the output of the below query: SELECT COUNT(*) FROM test_count;

• 7

• 6

• 10

• Throws exception because COUNT function doesn’t work with NULL values

Consider the following schema: SUPPLIERS(SupplierID, SupplierName, Address) Which SQL statement is used to REVOKE ALL privilege on the SUPPLIERS in the schema to the user ‘Manager’?

• REVOKE ALL ON SUPPLIERS FROM Manager

• GRANT ALL ON SUPPLIERS TO Manager

• REVOKE ALL ON SUPPLIERS TO Manager

• REVOKE ALL ON SUPPLIERS

An ACID transaction is one that is:

• Atomic

• Consistent

• Isolated

• Durable

• All of the above