DataStax Cassandra Developer Certification Certification Questions and Answer (Dumps and Practice Questions)

Question : . Ongoing repair operations in Cassandra ensure that all replicas of a row will eventually be _________

1. Durable

2. Active

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4. isolated

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Explanation: : Consistency refers to how up-to-date and synchronized all replicas of a row of Cassandra data are
at any given moment. Ongoing repair operations in Cassandra ensure that all replicas of a row will eventually be consistent.
Repairs work to decrease the variability in replica data, but constant data traffic through a widely distributed system can
lead to inconsistency (stale data) at any given time

Question : As per the CAP theorem, Cassandra is a ________ database

1. CA

2. AP

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4. CAP

Correct Answer : Get Lastest Questions and Answer :
Explanation: Consistency refers to how up-to-date and synchronized all replicas of a row of Cassandra data are at
any given moment. Ongoing repair operations in Cassandra ensure that all replicas of a row will eventually be consistent.
Repairs work to decrease the variability in replica data, but constant data traffic through a widely distributed system can
lead to inconsistency (stale data) at any given time. Cassandra is a AP system according to the CAP theorem, providing high
availability and partition tolerance. Cassandra does have flexibility in its configuration, though, and can perform more like
a CP (consistent and partition tolerant) system according to the CAP theorem, depending on the application requirements. Two
consistency features are tunable consistency and linearizable consistency.

Question : You can tune Cassandra's consistency level ____________

1. per-operation

2. set it globally for a cluster

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4. 1 and 2

5. 1,2 and 3

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Explanation: To ensure that Cassandra can provide the proper levels of consistency for its reads and writes,
Cassandra extends the concept of eventual consistency by offering tunable consistency. You can tune Cassandra's consistency
level per-operation, or set it globally for a cluster or datacenter. You can vary the consistency for individual read or write
operations so that the data returned is more or less consistent, as required by the client application. This allows you to
make Cassandra act more like a CP (consistent and partition tolerant) or AP (highly available and partition tolerant) system
according to the CAP theorem, depending on the application requirements.

Related Questions

Question : When multiple occurrences of data match a condition in a WHERE clause, Cassandra selects the most-frequent
occurrence of a condition for processing first for efficiency.

1. True
2. False

Question : You have been given two separate csv file as below.

course.csv : with following sample data

62c36092-82a1-3a00-93d1-46196ee77204, cassandra,{nosql,bigdata},

subscriber.csv (All the subscriber of the training course, it is possible a single company can have multiple user)
62c36092-82a1-3a00-93d1-46196ee77204, {hadoopexam@gmail.com, admin@hadoopexam.com} , Amit Jain

Which of the following is correct way to accommodate these data in Cassandra table?

A.
CREATE TABLE HADOOPEXAM {
course_id timeuuid,
title text,
Category set
}

CREATE TYPE SUBSCRIBER_TYPE {
course_id timeuuid,
emails set,
name text
}

ALTER TABLE HADOOPEXAM add SUBSCRIBER frozen;

B.

CREATE TYPE SUBSCRIBER_TYPE {
course_id timeuuid,
emails set,
name text
}

CREATE TABLE HADOOPEXAM {
course_id timeuuid,
title text,
Category set,
SUBSCRIBER SUBSCRIBER_TYPE
}

C.
CREATE TABLE SUBSCRIBER_TYPE {
course_id timeuuid,
emails set,
name text
}

CREATE TABLE HADOOPEXAM {
course_id timeuuid,
title text,
Category set,
SUBSCRIBER SUBSCRIBER_TYPE
}

D. CREATE TABLE SUBSCRIBER_TYPE {
course_id timeuuid,
emails map,
name text
}

CREATE TABLE HADOOPEXAM {
course_id timeuuid,
title text,
Category map,
SUBSCRIBER SUBSCRIBER_TYPE
}

1. A,B
2. B,C
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4. A,D
5. B,D

Question : Cassandra counters are always % accurate.

1. True
2. False

Question : Which of the following command will help you to run a cql file storing all cql commands?

1. SOURCE filename.cql

2. EXECUTE filename.cql

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4. FIRE filename.cql

5. COMMIT filename.cql

Question : . Which of the following is correct statement with regards to Counter?

A. A counter column value is a 64-bit signed integer.
B. You cannot set the value of a counter, which supports two operations: increment and decrement.
C. To generate sequential numbers for surrogate keys, use the counter type.
D. You can create an index on a counter column

1. A,B
2. B,C
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4. A,D
5. B,D

Question : You have been given below table definition

CREATE TABLE reviews (
review_id text,
downcount int,
upcount int,
creation_date timestamp,
PRIMARY KEY (review_id)
)

Now you want to update the upcount value by 1, hence you run the following query

update reviews set upcount = upcount +1 where review_id='123456';

What do you expect, out of this ?

1. It will successfully increment upcount by 1 for review_id='123456'

2. Update will be successful, but upcount will not be incremented by 1.

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4. Creation of table statement will fail.