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SQL for Top Customers
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SQL for Top Customers

EasySQL · PostgreSQL

Problem

Business Context

Coalition Greenwich wants to identify its highest-revenue institutional customers for the most recently completed reporting quarter. Assume the reporting date is April 15, 2025, so the last completed calendar quarter is January 1 through March 31, 2025.

Task

Write a PostgreSQL query that returns the top 10 customers by completed-order revenue during Q1 2025.

Requirements

  1. Join customers to orders using customer_id.
  2. Include only orders with status = 'completed' and an order_date from 2025-01-01 inclusive through 2025-04-01 exclusive.
  3. Aggregate revenue per customer, sort from highest to lowest revenue, and return at most 10 customers. Use customer_id as a deterministic tie-breaker.

Schema

customers
ColumnTypeDescription
customer_idPKINTEGERUnique customer identifier
customer_nameVARCHAR(120)Institutional customer name
regionVARCHAR(40)Customer operating region
orders
ColumnTypeDescription
order_idPKINTEGERUnique order identifier
customer_idINTEGERCustomer associated with the order
order_dateDATEDate the order was placed
statusVARCHAR(20)Order lifecycle status
revenueNUMERIC(12,2)Revenue attributed to the order
Tablescustomersorders
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