HDFC Bank Data Engineer Interview Questions, Process, and Tips

Q1. I was asked to write code and some scenario based question on Big Data etc
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2nd with VP which is easy but he seems not okay with my ECTC

Q1. What are joins of sql
Ans. 
Joins in SQL are used to combine rows from two or more tables based on a related column between them.
• Joins are used to retrieve data from multiple tables based on a related column

• Common types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column
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Q2. Explain about self join
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Self join is a SQL technique where a table is joined with itself to compare rows within the same table.
• Self join is used when we want to compare rows within the same table.

• It requires aliasing the table with different names to differentiate between the two instances.

• Commonly used in hierarchical data structures or when comparing related records.
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Q1. Explain spark stages and tasks
Ans. 
Spark stages are a collection of tasks that are executed together to perform a specific computation.
• Stages are created based on the transformations and actions in a Spark job.

• Each stage consists of a set of tasks that can be executed in parallel.

• Stages are divided into two types: narrow (one-to-one) and wide (one-to-many) transformations.

• Tasks within a stage are executed on different partitions of the data in parallel.

• ...read more
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Q2. Sql windoq questions
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Q1. Advance delta table optimizatoins
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Q2. Data modelling in previous project
Ans. 
Implemented data modelling using star schema in a retail analytics project.
• Designed star schema to optimize query performance

• Used fact and dimension tables to organize data

• Implemented ETL processes to populate the data warehouse

• Utilized tools like SQL, Python, and Apache Spark for data modelling
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Q1. What are the windows functions in sql
Ans. 
Window functions in SQL are used to perform calculations across a set of rows that are related to the current row.
• Window functions are used to calculate running totals, moving averages, and rank values.

• They are applied to a set of rows defined by an OVER clause.

• Examples of window functions include ROW_NUMBER, RANK, DENSE_RANK, and NTILE.
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Q2. Explain CTE in detail
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CTE stands for Common Table Expression, a temporary named result set that can be referenced within a SELECT, INSERT, UPDATE, or DELETE statement.
• CTE is defined using the WITH keyword followed by a name and a SELECT statement.

• It can be used to simplify complex queries, improve readability, and reduce code duplication.

• CTE can also be recursive, allowing for hierarchical queries.

• Example: WITH sales AS (SELECT * FROM order...read more
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Q1. What is your expected salary
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