SQL Exercise: Find largest number of orders booked by the customer
SQL Formatting Output: Exercise-9 with Solution
From the following table, write a SQL query that counts the unique orders and the highest purchase amount for each customer. Sort the result-set in descending order on 2nd field. Return customer ID, number of distinct orders and highest purchase amount by each customer.
Sample table: orders
Sample Solution:
SELECT customer_id, COUNT(DISTINCT ord_no),
MAX(purch_amt)
FROM orders
GROUP BY customer_id
ORDER BY 2 DESC;
Output of the Query:
customer_id count max 3002 3 5760.00 3009 2 2480.40 3005 2 948.50 3004 1 1983.43 3001 1 270.65 3007 1 2400.60 3008 1 250.45 3003 1 75.29
Code Explanation:
The said query in SQL that retrieves the customer id, count of distinct order numbers, and maximum purchase amount from the 'orders' table.
It is ordered by the number of distinct order numbers in descending order and grouped by the "customer_id" column within the result set.
This query returns the customer with the highest number of unique orders first and shows their customer id, the count of their unique orders, and the maximum amount spent on a single order.
Relational Algebra Expression:

Relational Algebra Tree:

Explanation:

Visual presentation:

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Previous SQL Exercise: Display customer name, city and grade by highest grade.
Next SQL Exercise: Purchase amount and commission for the last order.
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