SQL Exercises: Find the highest purchase amount each customer ordered

SQL Aggregate Functions: Exercise-10 with Solution

From the following table, write a SQL query to find the highest purchase amount ordered by each customer on a particular date. Return, order date and highest 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 combination of 'customer_id' and 'ord_date' from the 'orders' table.
SELECT customer_id, ord_date, MAX(purch_amt)
-- Specifies the table from which to retrieve the data (in this case, 'orders').
FROM orders
-- Groups the result set by the 'customer_id' and 'ord_date' columns.
GROUP BY customer_id, ord_date;

Output of the Query:

customer_id	ord_date	max
3002		2012-10-05	65.26
3003		2012-08-17	75.29
3005		2012-10-05	150.50
3007		2012-07-27	2400.60
3009		2012-08-17	110.50
3001		2012-09-10	270.65
3002		2012-09-10	5760.00
3005		2012-09-10	948.50
3009		2012-10-10	2480.40
3008		2012-06-27	250.45
3004		2012-10-10	1983.43
3002		2012-04-25	3045.60

Code Explanation:

The said SQL query retrieves the customer id, order date, and the maximum purchase amount for each combination of customer id and order date in the 'orders' table. The result will be grouped by customer id and order date.

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