SQL (Structured Query Language) is used to store, retrieve, update, and analyze data from relational databases.

Difference between WHERE and HAVING?

WHERE filters rows before aggregation. HAVING filters after aggregation.

Difference between DELETE, TRUNCATE, and DROP?

DELETE: removes selected rows. TRUNCATE: removes all rows (faster). DROP: deletes the table itself.

What is a primary key?

A column that uniquely identifies each row and cannot be NULL.

What is a foreign key?

A column that references a primary key in another table to maintain relationships.

Difference between INNER JOIN and LEFT JOIN?

INNER JOIN: only matching rows. LEFT JOIN: all left table rows + matched right rows.

What is a RIGHT JOIN?

Returns all rows from the right table and matching rows from the left.

What is a FULL OUTER JOIN?

Returns all rows from both tables, matched or unmatched.

When would you use a SELF JOIN?

When a table needs to be joined with itself (e.g., employee-manager hierarchy).

Difference between JOIN and UNION?

JOIN: combines columns. UNION: combines rows.

What does GROUP BY do?

Groups rows to perform aggregate functions like COUNT, SUM, AVG.

Can you use SELECT columns without GROUP BY?

No, unless the column is part of an aggregate function.

Difference between COUNT(*) and COUNT(column)?

COUNT(*): counts all rows. COUNT(column): ignores NULL values.

How to find duplicate records?

Use GROUP BY with HAVING COUNT(*) > 1.

How to find the second highest salary?

Use ORDER BY with LIMIT or a subquery.

A query inside another query, used for filtering or calculations.

Difference between subquery and CTE?

Subquery: inline, less readable. CTE (WITH): reusable and cleaner.

When should you use a CTE?

For complex logic, repeated queries, or readability.

Can a subquery return multiple rows?

Yes, when used with IN, ANY, or EXISTS.

What is EXISTS used for?

Checks if at least one row exists, faster than IN in large datasets.

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SQL for PMs

SQL for Product Managers

Master essential SQL queries every PM needs for data-driven decision making. From basics to advanced analytics with code examples.

60 Questions

10 Topics

Code Examples

SQL Cheat Sheet for PM Interviews

The most common SQL concepts asked in product manager interviews, with the question patterns interviewers use.

SELECT & WHERE

Pull metrics for a specific segment, e.g. orders last 30 days.

JOINs

Combine users with events or orders to study behavior across tables.

GROUP BY & HAVING

Compute DAU/MAU, retention and conversion by cohort.

Subqueries & CTEs

Break funnel analysis into readable, staged queries.

Window Functions

Rank users, running totals and period-over-period growth.

Query Performance

Explain indexes and why a slow dashboard query is slow.

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SQL Interview Questions and Answers

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Why SQL Matters for Product Managers

SQL is an essential skill for modern Product Managers. While you don't need to be a data engineer, understanding how to query databases enables you to make data-driven decisions without depending on analysts.

Key SQL Concepts for PMs

Basics: Understanding SELECT, WHERE, and basic filtering is fundamental. These allow you to pull specific data points for quick analysis.

Joins: Combining data from multiple tables is crucial for understanding user behavior across different touchpoints—from signup to purchase to retention.

Aggregations: GROUP BY and HAVING let you segment users, calculate metrics like DAU/MAU, and identify patterns in your data.

Window Functions: These are game-changers for analytics—running totals, cohort analysis, ranking users, and comparing periods become straightforward.

Master these concepts, and you'll be able to answer critical product questions independently. Browse our PM jobs to find opportunities where these skills are valued.

SQL for Product Managers

SQL Cheat Sheet for PM Interviews

SELECT & WHERE

JOINs

GROUP BY & HAVING

Subqueries & CTEs

Window Functions

Query Performance

SQL Interview Questions and Answers

BasicsWhat is SQL?

What is SQL?

BasicsDifference between WHERE and HAVING?

Difference between WHERE and HAVING?

BasicsDifference between DELETE, TRUNCATE, and DROP?

Difference between DELETE, TRUNCATE, and DROP?

BasicsWhat is a primary key?

What is a primary key?

BasicsWhat is a foreign key?

What is a foreign key?

JoinsDifference between INNER JOIN and LEFT JOIN?

Difference between INNER JOIN and LEFT JOIN?

JoinsWhat is a RIGHT JOIN?

What is a RIGHT JOIN?

JoinsWhat is a FULL OUTER JOIN?

What is a FULL OUTER JOIN?

JoinsWhen would you use a SELF JOIN?

When would you use a SELF JOIN?

JoinsDifference between JOIN and UNION?

Difference between JOIN and UNION?

AggregationsWhat does GROUP BY do?

What does GROUP BY do?

AggregationsCan you use SELECT columns without GROUP BY?

Can you use SELECT columns without GROUP BY?

AggregationsDifference between COUNT(*) and COUNT(column)?

Difference between COUNT(*) and COUNT(column)?

AggregationsHow to find duplicate records?

How to find duplicate records?

AggregationsHow to find the second highest salary?

How to find the second highest salary?

Subqueries & CTEsWhat is a subquery?

What is a subquery?

Subqueries & CTEsDifference between subquery and CTE?

Difference between subquery and CTE?

Subqueries & CTEsWhen should you use a CTE?

When should you use a CTE?

Subqueries & CTEsCan a subquery return multiple rows?

Can a subquery return multiple rows?

Subqueries & CTEsWhat is EXISTS used for?

What is EXISTS used for?

Window FunctionsWhat are window functions?

What are window functions?

Window FunctionsDifference between RANK() and DENSE_RANK()?

Difference between RANK() and DENSE_RANK()?

Window FunctionsWhat does ROW_NUMBER() do?

What does ROW_NUMBER() do?

Window FunctionsWhat is PARTITION BY?

What is PARTITION BY?

Window FunctionsUse case of window functions for PMs?

Use case of window functions for PMs?

PerformanceWhat is an index?

What is an index?

PerformanceWhen should you avoid indexes?

When should you avoid indexes?

PerformanceDifference between INNER JOIN and WHERE EXISTS?

Difference between INNER JOIN and WHERE EXISTS?

PerformanceHow do you handle NULL values?

How do you handle NULL values?

PerformanceOne SQL metric every PM should know?

One SQL metric every PM should know?

Practical BasicsCode ExampleWrite a query to find all unique job titles from the employees table.

Write a query to find all unique job titles from the employees table.

Practical BasicsCode ExampleSelect all details of customers who live in 'New York' or 'London'.

Select all details of customers who live in 'New York' or 'London'.

Practical BasicsCode ExampleFind all products that start with the letter 'A'.

Find all products that start with the letter 'A'.

Practical BasicsCode ExampleFind all orders where the shipping_date is missing (not yet shipped).

Find all orders where the shipping_date is missing (not yet shipped).

Practical BasicsCode ExampleCount the total number of orders placed in 2023.

Count the total number of orders placed in 2023.

Practical BasicsCode ExampleFind the total sales (revenue) for each product category.