SQL Exercises: Customer details and purchases over a certain amount

SQL Aggregate Functions: Exercise-16 with Solution

From the following table, write a SQL query to find the maximum order (purchase) amount for each customer. The customer ID should be in the range 3002 and 3007(Begin and end values are included.).Filter the rows for maximum order (purchase) amount is higher than 1000. 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.
-- The result set is then further filtered to only include rows where the maximum 'purch_amt' is greater than 1000.
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
-- Filters the grouped results to only include those where the maximum 'purch_amt' is greater than 1000.
HAVING MAX(purch_amt) > 1000;

Output of the Query:

customer_id	max
3002		5760.00
3007		2400.60
3004		1983.43

Code Explanation:

The given SQL query will retrieve the customer_id as well as the maximum purchase amount (purch_amt) for customers with an ID between 3002 and 3007, but this will only work if the maximum purchase amount exceeds 1000 from the 'orders' table.
The "HAVING" clause filters the result set by only showing customers whose maximum purchase amount is greater than 1000. The result will show the maximum purchase amount made by each customer in the specified range, with the customer_id being grouped together.

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