PayU Payments Lead Data Engineer Interview Questions and Answers

Aptitude test consists of 3 sections Quant , VA and logical
total time was 45 mins

Q1. What are the different types of commands in sql
Ans. 
Different types of commands in SQL include Data Definition Language (DDL), Data Manipulation Language (DML), Data Control Language (DCL), and Transaction Control Language (TCL).
• DDL commands are used to define the structure of database objects such as CREATE, ALTER, DROP.

• DML commands are used to manipulate data in the database such as SELECT, INSERT, UPDATE, DELETE.

• DCL commands are used to control access to data in the ...read more
Answered by AI
Add your answer
Q2. Difference between union and union all
Ans. 
Union combines and removes duplicates, Union All combines without removing duplicates.
• Union combines result sets and removes duplicates

• Union All combines result sets without removing duplicates

• Union is slower than Union All as it involves removing duplicates

• Union All is faster than Union as it does not remove duplicates
Answered by AI
Add your answer

Q1. What is datawarehouse
Ans. 
A datawarehouse is a centralized repository that stores integrated and structured data from multiple sources for analysis and reporting.
• Datawarehouse stores historical data for analysis

• It is used for decision-making and business intelligence

• Data is extracted, transformed, and loaded (ETL) into the datawarehouse

• Examples: Amazon Redshift, Snowflake, Google BigQuery
Answered by AI
Add your answer
Q2. How to open multiple sessions in postgresql
Ans. 
To open multiple sessions in PostgreSQL, you can use multiple connections from different clients.
• Use different client applications to connect to the PostgreSQL database with different credentials

• Each client connection will create a separate session in PostgreSQL

• You can also use connection pooling to manage multiple sessions efficiently
Answered by AI
Add your answer
Q3. How to flatten json
Ans. 
Flattening JSON involves converting nested JSON structures into a flat key-value format.
• Use a programming language with built-in functions for flattening JSON, such as Python's json_normalize() function.

• Recursively iterate through the JSON structure to extract all nested key-value pairs.

• Map each nested key to a flat key by joining the parent keys with a separator, such as a dot.

• Handle arrays by creating separate keys f
Answered by AI
Add your answer
Q4. How to flatten xml in python
Ans. 
Use the xmltodict library in Python to flatten XML data structures.
• Install the xmltodict library using pip install xmltodict

• Use xmltodict.parse() to convert XML data to a Python dictionary

• Use json.dumps() to convert the dictionary to a JSON string for a flattened structure
Answered by AI
Add your answer
Q5. How to do self join
Ans. 
Self join is used to join a table with itself to compare rows within the same table.
• Use the same table name for both instances in the query

• Specify aliases for each instance of the table to differentiate them

• Use a join condition to specify how the rows should be matched
Answered by AI
Add your answer