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

Question : When you are designing table in Cassandra, which is most important?

1. How data is structured.

2. How many columns in a row

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4. It depends on the query, what query we are going to execute against the data.


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Explanation: Data modeling in Cassandra uses a query-driven approach, in which specific queries are the key to
organizing the data. Cassandra's database design is based on the requirement for fast reads and writes, so the better the
schema design, the faster data is written and retrieved. Queries are the result of selecting data from a table; schema is the
definition of how data in the table is arranged.




Question : You have defined following table

CREATE TABLE TRINING_COURSE (
id uuid,
course_sequence int,
course_id uuid,
title text,
category text,
trainer text,
PRIMARY KEY (id, course_sequence ) );

Which of the following is a valid Query on this table ?

1. SELECT * FROM playlists;

2. SELECT album, title FROM TRINING_COURSE WHERE trainer = 'HadoopExam';

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4. 1 and 3
5. 1,2 and 3


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Explanation: Cassandra will reject query in option 2 because the query requires a sequential scan across the
entire dataset, because trainer is not a partition key or clustering column.

If you have created below index, then you can query based on trainer.

CREATE INDEX ON TRINING_COURSE( trainer );





Question : Select the correct statement?

1. The partition key determines which node stores the data.

2. partition key is responsible for data distribution across the nodes.

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4. 1 and 2

5. 1,2 and 3


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Explanation: A compound primary key consists of the partition key and one or more additional columns that
determine clustering. The partition key determines which node stores the data. It is responsible for data distribution across
the nodes. The additional columns determine per-partition clustering. Clustering is a storage engine process that sorts data
within the partition.

Related Questions

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Question : You have been given below relationship for the HadoopExam Inc employee


Now find the correct table design for given query access pattern?

Where employee_id=?



1. A
2. B
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4. D


Question : You have been given below conceptual data model for HadoopExam on-demand training access.


Please design logical table, which represent below query?

Query : Find the course_list for a given owner and will be ranged based on update_time (sort course_list by recently updated
first)




1. A
2. B
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4. D


Question : You have been given below conceptual data model for HadoopExam on-demand training access.



Please design logical table, which represent below query?

Query : Find all course_channels subscribed by a subscriber (sort course_channel by ascending order)



1. A
2. B
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4. D


Question :You have been given below logical table detail.


comments_by_user_id
user_id K
comment_date C
course_id C
user_email S
comment
course_name
description
Each user can post on average 1000 comments. SO what would be the number of values per partition we can expect.



1. 301
2. 300
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4. 100


Question : You have following table designed

Course_By_Author
Author_id K
Course_id C
Title
description

For each author_id, you will be copying entire course detail again. Assuming each course is created by 5 author.
Hence, each course detail will be copied 5 times. Is this an issue ?


1. Yes
2. No
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Question : You have been given below conceptual data model

And you have below Access pattern, which of the following is valid table design

where rating=? and publish_date=?


1. A
2. B
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4. D