The Ones Who Return

A medium SQL interview practice problem on DataDriven. Write and execute real sql code with instant grading.

Domain

SQL

Difficulty

medium

Seniority

mid

Problem

Our member growth team suspects that a large share of the people who buy from us try the service exactly once and never come back, while a smaller core keeps returning again and again, and before the quarterly retention review they want one anchor number to ground that story. Using the complete purchase history, work out what share of the entire member base counts as repeat buyers, meaning any member who shows up with more than a single purchase to their name, and express that share as a percentage of all members rounded to two decimal places.

Summary

One purchase is a trial. Two is a habit. Find how many members formed one.

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