coders.sh *

Loading Developers Heaven

The Session Stitcher

Mission brief

Challenge Briefing

Medium

Subqueries
Data Normalization

A user navigated anonymously, then logged in. Find the total number of page views for user_id = 42 by combining views where user_id = 42 AND views from the same device_id when user_id was NULL.

The Session Stitcher

Stitch anonymous and logged-in sessions using device_id.

The Narrative

A user navigated anonymously, then logged in. Find the total number of page views for user_id = 42 by combining views where user_id = 42 AND views from the same device_id when user_id was NULL.

Schema Diagram

page_views

view_idINT

device_idVARCHAR

user_idINT

Challenge a Friend

One SQL table. One SQL condition.
Still tricky for most developers.

SQL Editor

Terminal Output

Initializing Database Engine v1.8.0...

Write a SQL query, then click Run Query

Keep practicing

Try another challenge

Similar difficulty and topics — pick up where you left off or stretch your SQL skills.

View all

Title	Complexity	Status	Solve
The Skimming Intern	Medium	Not solved	Solve
Git Blame Detective	Medium	Not solved	Solve
The Shadow Follower	Hard	Not solved	Solve