SQL Exercises: Highest purchase amount from customers

Last update on February 11 2025 08:02:10 (UTC/GMT +8 hours)

From the following table, write a SQL query to determine the maximum order amount for each customer. The customer ID should be in the range 3002 and 3007(Begin and end values are included.). Return customer id and maximum purchase amount.

Sample table: orders

ord_no      purch_amt   ord_date    customer_id  salesman_id
----------  ----------  ----------  -----------  -----------
70001       150.5       2012-10-05  3005         5002
70009       270.65      2012-09-10  3001         5005
70002       65.26       2012-10-05  3002         5001
70004       110.5       2012-08-17  3009         5003
70007       948.5       2012-09-10  3005         5002
70005       2400.6      2012-07-27  3007         5001
70008       5760        2012-09-10  3002         5001
70010       1983.43     2012-10-10  3004         5006
70003       2480.4      2012-10-10  3009         5003
70012       250.45      2012-06-27  3008         5002
70011       75.29       2012-08-17  3003         5007
70013       3045.6      2012-04-25  3002         5001

Sample Solution:

-- This query retrieves the maximum 'purch_amt' value for each 'customer_id' from the 'orders' table.
-- It only includes rows where the 'customer_id' is between 3002 and 3007.
SELECT customer_id, MAX(purch_amt)
-- Specifies the table from which to retrieve the data (in this case, 'orders').
FROM orders
-- Filters the rows to only include those where the 'customer_id' is between 3002 and 3007.
WHERE customer_id BETWEEN 3002 AND 3007
-- Groups the result set by the 'customer_id' column.
GROUP BY customer_id;

Output of the Query:

customer_id	max
3002		5760.00
3007		2400.60
3004		1983.43
3003		75.29
3005		948.50

Code Explanation:

The said SQL query retrieves the customer_id and maximum purchase amount (purch_amt) for customers with id between 3002 and 3007 from the 'orders' table. The result will show the maximum purchase amount made by each customer in the specified range, with the customer_id being grouped together.

Relational Algebra Expression:

Relational Algebra Tree:

Explanation :

Visual presentation:

Practice Online

For more Practice: Solve these Related Problems:

• Write a SQL query to determine the maximum order amount for customers with IDs in the range 3001 to 3005.
• Write a SQL query to determine the maximum order amount for customers with IDs in the range 3003 to 3007, but only for orders placed in 2012.
• Write a SQL query to determine the maximum order amount for customers with IDs in the range 3004 to 3008, but only for orders with a purchase amount greater than 500.
• Write a SQL query to determine the maximum order amount for customers with IDs in the range 3002 to 3006, but only for customers with a grade of 200 or higher.

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