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

Question : Which all are true for Cassandra data modeling principal?

A. You must know your data
B. You know all your queries in advance
C. Wherever required de-normalize your data
D. You can store duplicate data


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

Correct Answer : Get Lastest Questions and Answer :
Explanation: These all are the data modeling principal in Cassandra

know your data in advance.
know your queries, you must aware what all queries are going to be executed on your data. Hence, find below
partition per query - ideal
partition+ per query - acceptable
ex. find movies that match one of multiple genres
table scan - anti-pattern
multi-table - anti-pattern
ex. retrieve all data in a database
nest data - denormalization
organizes multiple entities into a single partition
supports partition per query access
mechanisms
clustering columns
collection columns
user-defined type columns
duplicate data - denormalization
better than join
join on write





Question : In Cassandra, following scenarios can be considered as an ideal.

To fetch the data, Query needs to access all the partitions in a table, to retrieve results.


1. True
2. False

Correct Answer : Get Lastest Questions and Answer :
Explanation: Its not at all correct, it is considered worst design in Cassandra. Ideal case is your query must
read one partition and return the required result.




Question : Cassandra prefer space compare to time , while designing data modeling?

1. True
2. False

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Explanation: Yes, in Cassandra database , it is ok you duplicate data and acquire more space. Because, query
response time is more important the space and data join will be completely avoided.

Related Questions

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Question : The purpose of clustering key is to store row data in sorted order.

1. True
2. False


Question : You have been given below table definition

CREATE TABLE HADOOEXAM(

COURSE_TITLE text,
COURSE_ADDED_YEAR int,
COURSE_ADDED_DATE timestamp,
COURSE_DETAIL text,
USER_ID UUID,
COURSE_ID TIMEUUID,
PRIMARY KEY ((COURSE_TITLE,COURSE_ADDED_YEAR)));

What would be the result, when you run the below query?

SELECT * FROM HADOOEXAM WHERE COURSE_TITLE='CASSANDRA' ;

1. It will return all the courses which matches with the COURSE_TITLE='CASSANDRA'

2. It will return all the courses which is stored in the same partition where record for
COURSE_TITLE='CASSANDRA' stored

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4. This will say invalid query



Question : You have below tables defined with all the default Cassandra behavior. This table is empty
CREATE TABLE HADOOEXAM(

COURSE_TITLE text,
COURSE_ADDED_YEAR int,
COURSE_ADDED_DATE timestamp,
COURSE_DETAIL text,
USER_ID UUID,
COURSE_ID TIMEUUID,
PRIMARY KEY ((COURSE_TITLE)));

Now you fire the following query

UPDATE HADOOEXAM
SET COURSE_DETAIL ='HadoopExam Learning Resources'
WHERE COURSE_TITLE='CASSANRA' ;

What would happen?

1. It will throw error as there is no matching data

2. It will insert a new record

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4. None of the above



Question : You have been given below table definition

CREATE TABLE HADOOEXAM(

COURSE_TITLE text,
COURSE_ADDED_YEAR int,
COURSE_ADDED_DATE timestamp,
COURSE_DETAIL text,
USER_ID UUID,
COURSE_ID TIMEUUID,
PRIMARY KEY ((COURSE_TITLE),COURSE_ADDED_YEAR)));

What would be the result, when you run the below query?

SELECT * FROM HADOOEXAM WHERE COURSE_TITLE='CASSANDRA' AND COURSE_ADDED_YEAR=2017;

What is the expected result?

1. It will return all the courses which matches with the COURSE_TITLE='CASSANDRA' AND
COURSE_ADDED_YEAR=2017

2. It will return all the courses which is stored in the same partition where record for
COURSE_TITLE='CASSANDRA' stored

3. Access Mostly Uused Products by 50000+ Subscribers

4. This will say invalid query



Question : You have been given below table definition

CREATE TABLE HADOOEXAM(

COURSE_TITLE text,
COURSE_ADDED_YEAR int,
COURSE_ADDED_DATE timestamp,
COURSE_DETAIL text,
USER_ID UUID,
COURSE_ID TIMEUUID,
PRIMARY KEY ((COURSE_TITLE),COURSE_ADDED_YEAR)));

What would be the result, when you run the below query?

SELECT * FROM HADOOEXAM WHERE COURSE_TITLE='CASSANDRA' AND COURSE_ADDED_YEAR <=2017;

What is the expected result ?

1. It will return all the courses which matches with the COURSE_TITLE='CASSANDRA' AND
COURSE_ADDED_YEAR<=2017

2. It will return all the courses which is stored in the same partition where record for
COURSE_TITLE='CASSANDRA' stored

3. Access Mostly Uused Products by 50000+ Subscribers

4. This will say invalid query



Question : What does UPSERT means in Cassandra?

1. A failed UPDATE

2. A failed INSERT

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4. INSERTs may cause UPDATEs; UPDATEs may causes INSERTs