SQL Exercises: Higher purchase amount by the customer within a list

SQL Aggregate Functions: Exercise-14 with Solution

From the following table, write a SQL query to find the maximum order (purchase) amount based on the combination of each customer and order date. Filter the rows for maximum order (purchase) amount is either 2000, 3000, 5760, 6000. Return customer id, order date 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 combination of 'customer_id' and 'ord_date' from the 'orders' table.
-- It only includes rows where the maximum 'purch_amt' is one of the specified values (2000, 3000, 5760, 6000).
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
-- Filters the grouped results to only include those where the maximum 'purch_amt' is in the specified values (2000, 3000, 5760, 6000).
HAVING MAX(purch_amt) IN (2000, 3000, 5760, 6000);

Output of the Query:

customer_id	ord_date	max
3002		2012-09-10	5760.00

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, and only those groups with a maximum purchase amount equal to 2000, 3000, 5760, or 6000 will be returned.
The "HAVING" clause is used to specify the condition for the groups to be returned and the "IN" operator is used to define the set of values that the maximum purchase amount can be.

Explanation :

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