Gartner Data Specialist Interview Questions and Answers

Set of questions on english , aptitude , all are at easy level

Sql basics and some query questions

Q1. Why do u want to join zs ; what do u know about zs; where do u see urself after 5 years ; question on real life scenarios ;
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Q2. Question on real life scenarios
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Q1. Salary expectation
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Q2. When can u join
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Q1. Spark architecture
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Q2. Difference between coalesce and reparation
Ans. 
Coalesce is used to return the first non-null value among its arguments, while reparation is not a standard function in SQL.
• Coalesce is a standard SQL function, while reparation is not.

• Coalesce returns the first non-null value among its arguments.

• Reparation is not a standard SQL function and may refer to a custom function or process specific to a certain system or application.
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Q3. SQL question using Lag window function
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Q4. Same question in Pyspark
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Q5. Project and day to day activities
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Q1. Scenario based questions
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Q2. Gave details about work
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Some multiple choice, 2 sql and 2 python questions were asked

Q1. Tell me about you project
Ans. 
Developed a real-time data processing system for analyzing customer behavior
• Used Apache Kafka for streaming data ingestion

• Implemented data pipelines using Apache Spark for processing and analysis

• Utilized Elasticsearch for storing and querying large volumes of data

• Developed custom machine learning models for predictive analytics
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Q2. Optimising technique that you have used
Ans. 
I have used partitioning and indexing to optimize query performance.
• Implemented partitioning on large tables to improve query performance by limiting the data scanned

• Created indexes on frequently queried columns to speed up data retrieval

• Utilized clustering keys to physically organize data on disk for faster access
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Q1. Window partition question was asked
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Q2. Project related question
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Q1. Project related discussions
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Q2. Meduim level SQl and DSA
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Q1. This was data modelling round
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Q2. Design a uber data model
Ans. 
Uber data model design for efficient storage and retrieval of ride-related information.
• Create tables for users, drivers, rides, payments, and ratings

• Include attributes like user_id, driver_id, ride_id, payment_id, rating_id, timestamp, location, fare, etc.

• Establish relationships between tables using foreign keys

• Implement indexing for faster query performance
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Three sections are there 1) Aptitude Test 2) SQL 3) DSA

Q1. What is DSA , sorting , difference between array and linked list
Ans. 
DSA stands for Data Structures and Algorithms. Sorting is the process of arranging data in a particular order. Array is a data structure that stores elements of the same data type in contiguous memory locations, while linked list is a data structure that stores elements in nodes with pointers to the next node.
• DSA stands for Data Structures and Algorithms

• Sorting is the process of arranging data in a particular order

• Arra...read more
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Q2. Written a SQL query
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Q1. Coding question like add numbers
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Q2. Experience on your project
Ans. 
I have experience working on various data analysis projects, including market research, customer segmentation, and predictive modeling.
• Developed predictive models to forecast customer behavior and optimize marketing strategies

• Conducted market research to identify trends and opportunities for growth

• Performed customer segmentation analysis to target specific demographics with personalized marketing campaigns
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Q1. Power BI Difference between ALL() and ALLSELECTED()
Ans. 
ALL() ignores all filters in the query context, while ALLSELECTED() ignores only filters on columns in the visual.
• ALL() removes all filters from the specified column or table.

• ALLSELECTED() removes filters from the specified column or table, but keeps filters on other columns in the visual.

• Example: ALL('Table') would remove all filters on the 'Table' in the query context.

• Example: ALLSELECTED('Column') would remove filte...read more
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Q2. Excel Difference between COUNT() and COUNTA()
Ans. 
COUNT() counts only numeric values, while COUNTA() counts all non-empty cells.
• COUNT() counts only cells with numerical values.

• COUNTA() counts all non-empty cells, including text and errors.

• Example: COUNT(A1:A5) will count only cells with numbers, while COUNTA(A1:A5) will count all non-empty cells.
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Q1. Resume based questions like explain the projects that you have done.
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Q2. Sample dataset questions
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Q1. What is spark architecture
Ans. 
Spark architecture refers to the structure of Apache Spark, a distributed computing framework.
• Spark architecture consists of a cluster manager, worker nodes, and a driver program.

• The cluster manager allocates resources and schedules tasks across worker nodes.

• Worker nodes execute tasks in parallel and store data in memory or disk.

• The driver program coordinates the execution of tasks and manages the overall workflow.

• Spar...read more
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Q2. Optimizations of spark jobs
Ans. 
Optimizing Spark jobs involves tuning configurations, partitioning data, using appropriate data structures, and leveraging caching.
• Tune Spark configurations for optimal performance

• Partition data to distribute workload evenly

• Use appropriate data structures like DataFrames or Datasets

• Leverage caching to avoid recomputation

• Optimize shuffle operations to reduce data movement
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It was also very easy.

Q1. Basics of power bi and sql
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Q2. What are joins and types of join
Ans. 
Joins are used to combine rows from two or more tables based on a related column between them.
• Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• INNER JOIN returns rows when there is at least one match in both tables

• LEFT JOIN returns all rows from the left table and the matched rows from the right table

• RIGHT JOIN returns all rows from the right table and the matched rows from the left table

• FULL JOIN...read more
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Q3. How to add date table in power bi
Ans. 
To add a date table in Power BI, you can create a new table with a list of dates and relationships with other tables.
• Create a new table in Power BI with a list of dates

• Add columns for day, month, year, etc. for additional analysis

• Establish relationships between the date table and other tables in the data model
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Q1. Sql scenario based question on joins
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Q2. Window function questions
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Q3. Performance tuning
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Q4. Power bi dax question
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