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



Question : Entities and relationships, equality search attributes, inequality search attributes, ordering attributes, key
attributes. Is the correct order of mapping rule?
: Entities and relationships, equality search attributes, inequality search attributes, ordering attributes, key
1. True
2. False

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Explanation: Mapping Rules

Entities and relationships, equality search attributes, inequality search attributes, ordering attributes, key attributes.

To design a table schema, it is important to apply these
mapping rules in the context of a particular query and a
subgraph of the conceptual data model that the query deals
with. The rules should be applied in the same order as they
are listed above.




Question : Static columns are stored only once per partition?
: Static columns are stored only once per partition?
1. True
2. False

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Explanation: A static column is a special column that is shared by all the rows of the same partition. Let's take
an example: suppose that we want to store per-user bills that needs to be paid and keep a per-user balance amount of what
remains to be paid. The invariant we want to maintain is that the balance is always the sum of all unpaid bills:

CREATE TABLE bills (
user text,
balance int static,
expense_id int,
amount int,
description text,
paid boolean,
PRIMARY KEY (user, expense_id)
);





Question : Which is true with regards to Cassandra partition size
: Which is true with regards to Cassandra partition size
1. One of the measure of partition size are the number of values in a partition

2. One of the measure of partition size is partition size on disk

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4. 1 and 2

5. 1,2 and 3

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Explanation: For efficient operation, partitions must be sized within certain limits in Apache Cassandra. Two
measures of partition size are the number of values in a partition and the partition size on disk. The practical limit of
cells per partition is two billion. Sizing the disk space is more complex, and involves the number of rows and the number of
columns, primary key columns and static columns in each table. Each application will have different efficiency parameters, but
a good rule of thumb is to keep the maximum number of rows below 100,000 items and the disk size under 100 MB.


Related Questions

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



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 ?
 : You have defined following 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



Question : Select the correct statement?
 : 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



Question : Cassandra stores an entire row of data on a node by partition key. If you have too much data in a partition and
want to spread the data over multiple nodes, use a ________________

 : Cassandra stores an entire row of data on a node by partition key. If you have too much data in a partition and
1. Secondary Index

2. composite partition key.

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4. Single Column Primary key



Question : You have already defined a table named HADOOPEXAM, now you want to add unique collection of email address for
each primary key, which of the following is correct statement
 : You have already defined a table named HADOOPEXAM, now you want to add unique collection of email address for
1. ALTER TABLE HADOOPEXAM ADD emails set;

2. ALTER TABLE HADOOPEXAM ADD emails list;

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4. ALTER TABLE HADOOPEXAM ADD email1 text, email2 text, email3 text;



Question : . You have defined a table as below

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

ALTER TABLE TRINING_COURSE ADD emails set;

Which of the following is correct CQL to add new emailid for a training_course
 : . You have defined a table as below
1. ADD VALUE TO TRINING_COURSE IN emails = emails + {'hadoopexam@gmail.com'}
WHERE id = 62c36092-82a1-3a00-93d1-46196ee77204 AND course_sequence = 2;


2. UPDATE TRINING_COURSE SET emails = emails + {'hadoopexam@gmail.com'}
WHERE id = 62c36092-82a1-3a00-93d1-46196ee77204 AND course_sequence = 2;


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WHERE id = 62c36092-82a1-3a00-93d1-46196ee77204 AND course_sequence = 2;


4. UPDATE TRINING_COURSE SET emails = {emails, {'hadoopexam@gmail.com'}}
WHERE id = 62c36092-82a1-3a00-93d1-46196ee77204 AND course_sequence = 2;