Data AnalystInterview Questions & Answers
Prepare for your placement drives and technical screenings with these core questions and answers tailored for junior Data Analyst candidates.
Q1:What is the difference between a WHERE clause and a HAVING clause in SQL?
Answer: `WHERE` is used to filter individual database rows before group aggregates are calculated. `HAVING` is used to filter grouped records after the `GROUP BY` clause has aggregated the rows, commonly used alongside functions like `SUM()`, `AVG()`, or `COUNT()`.
Q2:Explain what data cleaning is and why it is important.
Answer: Data cleaning is the process of identifying and correcting errors, inconsistencies, duplicates, and missing values in raw datasets. It is crucial because dirty data leads to incorrect statistics and misleading business decisions. Clean data ensures accurate analytics and reliable predictive models.
Q3:What is a Left Join and how does it differ from an Inner Join?
Answer: An `INNER JOIN` returns only the matching rows present in both tables. A `LEFT JOIN` returns all rows from the left table, along with the matching rows from the right table. If there is no match in the right table, database cells return `NULL` values for the right table columns.
How to Answer Behavioral Interview Questions
When answering situational questions (like “tell me about a time you resolved a conflict”), always use the STAR method:
- Situation: Set the context and describe the background.
- Task: Explain the core challenge or goal you had to address.
- Action: Detail the specific steps you took to resolve it.
- Result: Highlight the positive outcome and what you learned.
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