TCS ETL Tester Interview Questions, Process, and Tips

Q1. SQL Basics and advanced
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Q2. Pyspark questions
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Q1. What are scd types
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SCD types refer to slowly changing dimensions used in data warehousing to track historical changes in data over time.
• SCD Type 1: Overwrites old data with new data, losing historical information.

• SCD Type 2: Keeps multiple versions of the same record, with a separate row for each change.

• SCD Type 3: Maintains both old and new values in the same record, with separate columns for each version.
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Q2. How you identify duplicates and how to find latest duplicate
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Identifying duplicates and finding the latest duplicate in ETL testing
• Identify duplicates by comparing key fields in the dataset

• To find the latest duplicate, look for the record with the highest timestamp or version number

• Use SQL queries or ETL tools to filter out duplicates and identify the latest one
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Q3. What is the difference between star schema and snowflake schme
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Star schema has a single fact table connected to multiple dimension tables directly, while snowflake schema has normalized dimension tables connected to each other.
• Star schema has denormalized dimension tables, making it easier to query but potentially less efficient for storage.

• Snowflake schema has normalized dimension tables, reducing redundancy but potentially making queries more complex.

• Star schema is more suitable...read more
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Q4. What are the test articrafts
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Test artifacts are documents or deliverables created during the testing process to ensure thorough testing and documentation.
• Test plan: outlines the testing approach, scope, resources, and schedule

• Test cases: detailed steps to be executed during testing

• Test scripts: automated scripts for regression testing

• Test data: sample data used for testing

• Defect reports: documentation of issues found during testing
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Q1. Two interviewer panel asked question related to joins store procedure etl architecture real time scenarios
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1) write a query to find the highly paid person between two tables

2)How to separate First and name last

3) Rank and dense rank

4)Facts and Dimensions