NIELIT Scientist –B Day -23 DataBase Quiz-2

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Question 1

In the tuple relational calculus P1 P2 is equivalent to

• A ¬(P1)VP2
• B ¬( ¬(P1)^ ¬(P2))
• C ¬(∃(P1∈( ¬P2))
• D ¬( ¬(P1)V ¬(P2))

Question 2

Which among the following schedules is an irrecoverable Schedule?

• A
• B
• C
• D

Question 3

What is the meaning of the following given SQL clause?
LIKE “%0%0%”

• AValue begins with two 0’s
• BValue ends with two 0’s
• CValue has ore than two 0’a
• DValue has atleast two 0’s in it,at any position

Question 4

Assume a office database of employee details
SELECT Emp_name,salary
FROM Emp_details
HAVING salary>30000
What is the error in above query?

• AThere is no HAVING clause in SQL
• BHaving clause is not used for filtering
• CHAVING clause is used without GROUP BY clause
• DNo error, it will result properly

Question 5

Consider the following partial Schedule S involving two transactions T1 and T2. Only the read and the write operations have been shown. The read operation on data item P is denoted by read (P) and the write operation on data item P is denoted by write (P).

Suppose that the transaction T1 fails immediately after time instance 9. Which one of the following statements is correct?

• AT2 must be aborted and then both T1 and T2 must be re-started to ensure transaction atomicity
• BSchedule S is non-recoverable and cannot ensure transaction atomicity
• COnly T2 must be aborted and then re-started to ensure transaction atomicity
• DSchedule S is recoverable and can ensure atomicity and nothing else needs to bed one

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