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SQL Basics in PostgreSQL

Ordering
Limiting the output
Eliminating duplicate results
Aggregation
Grouping
20. Find the average value in groups
HAVING: filtering and ordering groups
Let's practice

Instruction

That's right!

Let's study one more example of this kind:

SELECT
  customer_id,
  AVG(total_sum)
FROM orders
WHERE order_date >= '2019-01-01'
  AND order_date < '2020-01-01'
GROUP BY customer_id;

As you can see, we now use the function AVG(total_sum) which will count the average order value for each of our customers but only for their orders placed in 2019.

Exercise

For each department find the average salary in 2015.

Stuck? Here's a hint!

Type:

SELECT
  department,
  AVG(salary)
FROM employees
WHERE year = 2015
GROUP BY department;