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#0337
Days Between First and Last Event
MediumSQL24 min20 XP
Problem
Return user_id and active_span_days as days between first and last event.
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
events(user_id INTEGER, event_date TEXT)
Examples
Example 1
Inputuser 1 active from Jan 1 to Jan 6
Outputuser 1 span is 5 days
JULIANDAY converts dates to numeric day values.
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 active from Jan 1 to Jan 6
Expected[[1,5],[2,0]]
JULIANDAY converts dates to numeric day values.
Hidden Test Categories
Empty or missing matchesDuplicate rows or tiesNULL values where the pattern commonly breaks