Ace Your Next Data Analyst Interview With SQL.

• Ace Your Next Data Analyst Interview With SQL

Core SQL Foundations

• Explain the difference between WHERE and HAVING.
• What are the different types of SQL JOINs?
• Describe the difference between UNION and UNION ALL.
• What is the purpose of the CASE statement?
• How do you remove duplicate records from a query result?

Data Retrieval & Filtering

• How would you find the second highest salary from a table?
• Write a query to select all employees whose name starts with 'A'.
• How do you filter for records that contain a null value?
• Retrieve the top 5 most recent orders from a table.
• Explain how the LIKE operator is used with wildcards.

Aggregation & Grouping

• What is the difference between COUNT(*) and COUNT(column_name)?
• How do you calculate a cumulative sum or running total?
• Find the department with the highest average salary.
• Calculate the month-over-month sales growth percentage.
• Get a count of orders per customer for only those with more than 5 orders.

Advanced Query Techniques

• What is a correlated subquery and how does it work?
• Explain the purpose of Common Table Expressions (CTEs).
• How would you rank rows without using the RANK() function?
• Describe a scenario where you would use a self-join.
• Compare using a subquery versus a CTE for readability.

Data Modification & Management

• What is the difference between DELETE, TRUNCATE, and DROP?
• How would you update prices for a specific product category?
• Write a query to insert data from one table into another.
• Explain the concept of ACID properties in databases.
• What is a transaction and why is it important?

Window Functions Mastery

• Explain the difference between RANK, DENSE_RANK, and ROW_NUMBER.
• How do you use the LAG and LEAD functions?
• Calculate a 7-day moving average of sales using a window function.
• Partition data by department to calculate internal rankings.
• What is the frame clause in a window function?

Database Design & Theory

• What is the difference between a primary key and a unique key?
• Explain database normalization and its benefits.
• Describe the different types of relationships between tables.
• What is an index and how does it improve query performance?
• Define a foreign key and its role in relational databases.

Scenario-Based Problem Solving

• How would you find users who made purchases two days in a row?
• Design a query to identify the employee with the nth highest salary.
• Calculate the retention rate of users from one month to the next.
• How would you merge two tables with slightly different schemas?
• Describe your process for troubleshooting a slow-running query.