Dataford
Interview QuestionsInterview GuidesExperiencesCoaching
New
Pricing
Get started
Dataford
Popular roles
Software EngineerData AnalystData ScientistData EngineerBusiness AnalystAI EngineerMachine Learning EngineerProduct Manager
Browse
Browse All RolesEvery role hub, from analyst to MLBrowse All CompaniesCompany-specific interview loopsAll Interview GuidesThe full guide library
Top questions by role
Software EngineerData AnalystData ScientistData EngineerBusiness AnalystAI EngineerMachine Learning EngineerProduct Manager
Top questions by skill
SQLPythonStatisticsMachine LearningA/B TestingSystem DesignGenerative AIProduct SenseMetricsBehavioral
Browse all questions →Try a mock interview
Experiences
Practice
Mock InterviewsTimed interview simulations with feedbackCoaching1:1 coaching with people at your target companiesSuccess PathYour 6-week structured planModulesCurated lessons by topicWebinarsTalks from ex-Big Tech data leadsPlaygroundA free-form scratch editor
Learn
BlogInterview strategy and career adviceTech Job Market ReportHiring trends across data and AI rolesFor UniversitiesDataford for career centersAbout DatafordWho we are and how we build
Pricing
Build my plan
SQL Time-Window Aggregation
00:00
5 left

SQL Time-Window Aggregation

MediumSQL · PostgreSQL

Problem

Write a SQL query to aggregate user interaction data over a specific time window.

Use the users and interaction_events tables. Analyze events from 2025-01-01 00:00:00 inclusive through 2025-02-01 00:00:00 exclusive. Include every user, including users with no interactions in the time window. Treat missing durations as zero.

Output

  1. One row per user with user_id, user_name, interaction_count, total_duration_seconds, and last_interaction_at.
  2. Sort by interaction count descending, total duration descending, then user ID ascending.

Schema

users
ColumnTypeDescription
user_idPKINTUnique user identifier
user_nameVARCHAR(100)Display name of the user
interaction_events
ColumnTypeDescription
interaction_idPKINTUnique interaction event identifier
user_idINTUser identifier associated with the event
interacted_atTIMESTAMPTimestamp when the interaction occurred
event_typeVARCHAR(50)Type of user interaction
duration_secondsINTDuration of the interaction in seconds
Tablesusersinteraction_events
Interviewer

Your question is SQL Time-Window Aggregation. Start with the requirements and the two tables in the Question tab.

Run and submit as often as you like. When you're ready, talk me through your approach or go straight to the code.

You need to log in / sign up to run or submit.
CodePostgreSQL
Sign up free to run your codeLog inLn 1
Run your query to see results here.