DMC DMC ETL Processes & Data Warehousing 1 — Questions and Answers
Question 1: What does ETL stand for in data warehousing?
- Encode, Transfer, Load
- Extract, Transform, Load (Correct answer)
- Export, Translate, Link
- Evaluate, Test, Launch
Correct answer: Extract, Transform, Load
ETL stands for Extract, Transform, Load — the three-phase process of pulling data from sources, reshaping it, and loading it into a target system.
Question 2: Which ETL phase is responsible for data cleaning and reformatting?
- Extract phase
- Load phase
- Transform phase (Correct answer)
- Validate phase
Correct answer: Transform phase
The Transform phase handles data cleaning, reformatting, deduplication, and applying business rules before loading into the target warehouse.
Question 3: What is a 'staging area' in an ETL process?
- The final production data warehouse
- A temporary storage area where data is held between extraction and loading (Correct answer)
- The operational source database
- The production environment used for end-user analysis
Correct answer: A temporary storage area where data is held between extraction and loading
A staging area is temporary storage where extracted data is held and preprocessed before being loaded into the final data warehouse.
Question 4: What is 'incremental loading' in ETL?
- Reloading all source data from scratch on every ETL run
- Loading only new or changed records since the last ETL run (Correct answer)
- Loading records in alphabetical or sorted order
- Loading data exclusively during off-peak maintenance windows
Correct answer: Loading only new or changed records since the last ETL run
Incremental loading updates the warehouse by processing only new or modified records since the last run, reducing processing time and resource usage.
Question 5: What is the primary purpose of data profiling in ETL?
- To compress data for faster loading performance
- To analyze the content, quality, and structure of source data (Correct answer)
- To create user access profiles for data security
- To generate automated documentation for the ETL pipeline
Correct answer: To analyze the content, quality, and structure of source data
Data profiling analyzes source data to understand its content, quality, completeness, and structure before designing ETL transformation rules.
Question 6: What is 'data latency' in the context of an ETL pipeline?
- Corrupted data caused by network packet loss
- The delay between when data is generated in the source and when it is available in the warehouse (Correct answer)
- The time required to execute a complex SQL query
- The lag introduced by slowly changing dimension processing
Correct answer: The delay between when data is generated in the source and when it is available in the warehouse
Data latency is the time delay between when source data is created or updated and when that data becomes available for querying in the data warehouse.
DMC DMC ETL Processes & Data Warehousing 1
What does ETL stand for in data warehousing?