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#0359
Users With Consecutive Login Days
MediumSQL24 min20 XP
Problem
Return user_id values that have logins on two consecutive calendar days.
Why This Matters
SQL interviews usually test whether you can turn a business question into the right rows, grouping level, join type, and edge-case behavior.
Schema
logins(user_id INTEGER, login_date TEXT)
Examples
Example 1
Inputuser 1 logged in Jan 1 and Jan 2
Outputuser 1
The self-join checks for the next calendar day.
Constraints
- Return only the requested columns.
- Use deterministic ORDER BY when multiple rows are returned.
- Assume SQLite-compatible SQL unless the prompt states otherwise.
CodeSQL
Visible browser tests run here when available.
Testcases1 visible / 3 hidden categories
Core SQL case
Inputuser 1 logged in Jan 1 and Jan 2
Expected[[1]]
The self-join checks for the next calendar day.
Hidden Test Categories
Empty or missing matchesDuplicate rows or tiesNULL values where the pattern commonly breaks