Write conditional aggregation SQL queries

Q: How do I practice SQL interview questions?

PracHub provides an interactive SQL console where you can write and test queries against real database schemas. Get instant feedback and compare your solution with the expected output.

Q: What difficulty level is this coding question?

This is a medium difficulty Data Manipulation (SQL/Python) question, commonly asked during Onsite rounds at PayPal.

Q: What role is this question designed for?

This question is commonly asked for Data Scientist candidates at PayPal during technical interviews.

Question

##### Question

Write an SQL query to compute the total amount for rows satisfying a condition, comparing approaches that use SUM(CASE WHEN … THEN … END) versus a simple SUM with a WHERE filter. Rewrite the query from Question 1 using CASE WHEN for conditional aggregation. Given a grouped query, place an aggregation filter in the HAVING clause; explain whether the syntax works in MySQL and why.

PracHub · Accepted Answer

This question evaluates proficiency with conditional aggregation in SQL, including the use of SUM(CASE WHEN ...) versus filtering with WHERE and the implications of placing aggregation filters in HAVING for grouped queries, within the Data Manipulation (SQL/Python) domain.

Quick Overview

Write conditional aggregation SQL queries