gs gs117 Concurrency Control - Snapshot Isolation - Quiz No.1

gs gs117 Database Management System Quiz

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Question 1: Snapshot isolation is a particular type of ______________ scheme.

Concurrency-control

Concurrency-allowance

Redirection

Repetition-allowance

Question 2: Snapshot isolation is used to give

Transaction a snapshot of the database

Database a snapshot of the transaction

Database a snapshot of committed values in the transaction

Transaction a snapshot of the database and Database a snapshot of committed values in the transaction

Question 3: Lost update problem is

Second update overwrites the first

First update overwrites the second

The updates are lost due to conflicting problem

None of the mentioned

Question 4: Under first updater wins the system uses a __________ mechanism that applies only to updates.

Read

Locking

Beat

Question 5: When a transaction Ti attempts to update a data item, it requests a _________ on that data item.

Read lock

Update lock

Write lock

Chain lock

Question 6: Each of a pair of transactions has read data that is written by the other, but there is no data written by both transactions, is referred to as

Read skew

Update skew

Write lock

None of the mentioned

Question 7: An application developer can guard against certain snapshot anomalies by appending a ______ clause to the SQL select query.

For update

For read

For write

None of the mentioned

Question 8: Evaluate the CREATE TABLE statement:

CREATE TABLE products (product_id NUMBER(6) CONSTRAINT prod_id_pk PRIMARY KEY, product_name VARCHAR2(15));

Which statement is true regarding the PROD_ID_PK constraint?

It would be created only if a unique index is manually created first

It would be created and would use an automatically created unique index

It would be created and would use an automatically created no unique index

It would be created and remains in a disabled state because no index is specified in the command

Question 9: Evaluate the following CREATE SEQUENCE statement:

CREATE SEQUENCE seq1 START WITH 100 INCREMENT BY 10 MAXVALUE 200 CYCLE NOCACHE;

The sequence SEQ1 has generated numbers up to the maximum limit of 200. You issue the following SQL statement:
SELECT seq1.nextval FROM dual;
What is displayed by the SELECT statement?

100

an error

Question 10: In which scenario would you use the ROLLUP operator for expression or columns within a GROUP BY clause?

To find the groups forming the subtotal in a row

To create group-wise grand totals for the groups specified within a GROUP BY clause

To create a grouping for expressions or columns specified within a GROUP BY clause in one direction, from right to left for calculating the subtotals

To create a grouping for expressions or columns specified within a GROUP BY clause in all possible directions, which is cross-tabular report for calculating the subtotals