SQL Exercises: Find the average purchase amount of all orders

SQL Aggregate Functions: Exercise-2 with Solution

From the following table, write a SQL query to calculate the average purchase amount of all orders. Return average 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:

-- Calculating the average value of the 'purch_amt' column in the 'orders' table
SELECT AVG(purch_amt)
-- Specifying the table to retrieve data from ('orders')
FROM orders;

Output of the Query:

avg
1461.7650000000000000

Code Explanation:

The said SQL query retrieves the average of values in the "purch_amt" column from the 'orders' table. The "SELECT AVG (purch_amt)" statement specifies that the average of the values in the "purch_amt" column should be retrieved. The result of this query will be a single value that represents the average of all values in the "purch_amt" column in the 'orders' table.

Relational Algebra Expression:

Relational Algebra Tree:

Explanation:

visual presentation :

Practice Online

Query Visualization:

Duration:

Rows:

Cost:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous SQL Exercise: Find the total purchase amount for all orders.
Next SQL Exercise: Find the number of salesmen for each customer.