SQL AVG function

SQL AVG function is used to return the average value of an expression in the SELECT operator.

Syntax for AVG function in SQL

SELECT AVG(aggregate_expression_id)
FROM tabs
[WHERE conds]

Or syntax for AVG function when grouping results by one or more columns.

SELECT expression1_id, expression2_id, ... expression_n_id,
AVG(aggregate_expression_id)
FROM tabs
[WHERE conds]
GROUP BY expression1_id, expression2_id, ... expression_n_id;

where:

• expression1_id, expression2_id, …_n_id – Expressions which are not encapsulated in the AVG functions and must be included in the GROUP BY offer at the end of the SQL query
• aggregate_expression_id – This is the column or expression to be averaged.
• tabs – The tables from which you want to get the records. The FROM sentence must contain at least one table
• WHERE conds – Optional. These are the conditions that must be met to select records

Single Expression Example

For example, you may want to know the average value of all the items in the Clothing category.

SELECT AVG(cost) AS "Average Cost_id"
FROM prods
WHERE cat = 'Clothing_id';

In this example of the AVG SQL function, we have specified the alias “Average Cost_id” to the AVG(cost) expression. As a result, “Average Cost_id” will be displayed as the field name when returning the result set.

Using SQL DISTINCT

You can use SQL DISTINCT in AVG function. For example, instruction SELECT resulted below returns cumulative average cost of unique values of cost where the category – Clothing.

SELECT AVG(DISTINCT cost) AS "Average Cost_id"
FROM prods
WHERE category = 'Clothing_id';

If there were two values of $25, only one of these values would be used to calculate the AVG function.

Using formulas

expression_id contained in the AVG function does not necessarily have to be a single field. You can also use a formula. For example, you can get an average profit per product. The average profit is calculated as sale_price_id minus cost_id.

SELECT AVG(sale_price_id - cost_id) AS "Average Profit_id".
FROM prods;

You can also perform mathematical operation in AVG function. For example, you can define the average commission as 10% of sale_price_id.

SELECT AVG(sale_price_id * 0.10) AS "Average Commission_id".
FROM prods;

Using SQL GROUP BY

In some cases you will need to use the SQL GROUP BY offer with AVG function.

For example, you can also use the AVG function to return the department name and average sales (in a related department).

SELECT department_id,
AVG(sales_id) AS "Average Sales_id"
FROM ord_details
WHERE department_id > 10
GROUP BY department_id;

Sql Training Online – Sql Average Function