SQL AVG Function
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The AVG function is used to find the average value in an expression.
The syntax for the AVG function is,
SELECT AVG (<expression>)
<expression> can be a column name or an arithmetic operation. An arithmetic operation can include more than one column, such as ("column1" * "column2").
It is also possible to have one or more columns in addition to the AVG function in the SELECT statement. In those cases, these columns need to be part of the GROUP BY clause as well:
SELECT "column_name1", "column_name2", ... "column_nameN", AVG (<expression>)
GROUP BY "column_name1", "column_name2", ... "column_nameN";
We use the following table for our examples.
Example 1: AVG function on a column
To find the average sales amount, we type in,
SELECT AVG(Sales) FROM Store_Information;
687.5 represents the average value of all Sales entries: (1500+250+300+700) / 4.
Example 2: AVG function on an arithmetic operation
Assume that sales tax is 10% of the sales amount, we use the following SQL statement to get the average sales tax amount:
SELECT AVG(Sales*0.1) FROM Store_Information;
SQL will first calculate "Sales*0.1" and then apply the AVG function to the result for the final answer.
Example 3: AVG function with a GROUP BY clause
To get the average amount of sales for each store, we type in,
SELECT Store_Name, AVG(Sales) FROM Store_Information GROUP BY Store_Name;