Post by Sonal Holankar
Big Data Engineer | ETL Pipelines | SQL | Python | Apache Spark | Data Modeling | Data Pipelines | Cloud (AWS/Azure/GCP) | Big Data Enthusiast | Azure Databricks
šØ Data Engineering Interview Series: Most Asked SQL Questions šØ If you're preparing for a Data Engineer, SQL Developer, Analytics Engineer, or Data Analyst interview, these are the SQL topics that repeatedly appeared in my interviews. š¹ SQL Fundamentals ā DDL vs DML vs DCL vs TCL Commands ā Primary Key vs Unique Key ā NULL vs NOT NULL ā Delete vs Truncate vs Drop ā SQL Execution Order š¹ SQL Joins ā Inner Join ā Left Join ā Right Join ā Full Outer Join ā Self Join ā Cross Join ā Left Join vs Inner Join Coding Questions šø Find unmatched records from two tables šø Employee-Manager hierarchy queries šø Customer who never placed an order š¹ CTE & Subqueries ā Why are CTEs useful? ā CTE vs Subquery ā Recursive CTE ā Multiple CTEs in a single query š¹ SQL Set Operators ā UNION vs UNION ALL ā INTERSECT ā EXCEPT / MINUS š¹ Indexing & Performance ā SQL Query Optimization Techniques ā Clustered Index vs Non-Clustered Index ā Composite Index ā Covering Index ā When Indexes Hurt Performance? ā Explain Query Execution Plan š¹ Aggregations ā GROUP BY Questions ā HAVING vs WHERE ā GROUP BY vs HAVING ā COUNT(*) vs COUNT(Column) Coding Questions šø Find departments with more than 5 employees šø Calculate running totals šø Monthly sales aggregation š¹ Window Functions (Most Asked) ā ROW_NUMBER() ā RANK() ā DENSE_RANK() ā LEAD() ā LAG() ā FIRST_VALUE() ā LAST_VALUE() ā NTILE() Coding Questions šø 2nd Highest Salary šø Nth Highest Salary šø Top 3 salaries per department šø Remove duplicate records šø Latest record per customer šø Consecutive days login problem š¹ Date & Time Functions ā Current Date Functions ā Date Difference Calculations ā Month End Calculations ā Previous Month Data ā Rolling 7-Day Metrics Coding Questions šø Calculate employee tenure šø Find records from last 30 days šø Generate date series š¹ Frequently Asked SQL Coding Problems š„ Remove Duplicates from a Table š„ Show Duplicate Records š„ Top N Records š„ Top 100 Rows from a Table š„ Running Total š„ Moving Average š„ Pivot & Unpivot Data š„ Gap and Island Problems š„ Find Missing IDs š„ Customers with Consecutive Purchases š„ Highest Salary in Each Department š„ Find Employees Earning More Than Their Manager š¹ Advanced SQL Concepts ā Views vs Materialized Views ā Stored Procedures vs Functions ā Temporary Tables ā Transactions & ACID Properties ā Normalization vs Denormalization ā Star Schema vs Snowflake Schema #DataEngineering #SQL #SQLInterviewQuestions #DataEngineer #BigData #AnalyticsEngineer #Database #ETL #DataWarehouse #Snowflake #Databricks #ApacheSpark #InterviewPreparation #TechCareers #LearnSQL #DataCommunity