Row vs Columnar Storage

Problem

You are querying a database that holds 10 billion rows to find the average transaction amount. A row-oriented database scans all columns, whereas a columnar database reads only the transaction amount column. Write a query that outputs advantage with the value: "Columnar databases compress data heavily and reduce disk I/O for aggregations by storing each column's values sequentially on disk."

Database Schema

This problem acts as a scratchpad. You will write your own DDL/DML or conceptual queries, so there is no predefined schema.

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Solution