SQL Server AVG() Function

 The AVG() function in SQL Server is used to calculate the average value of a numeric column. It is an aggregate function, meaning it operates on a set of values and returns a single value.

Syntax

SELECT AVG(column_name)
FROM table_name
WHERE condition;

Key Points:

1. Numeric Data: The column used in the AVG() function must contain numeric data types, such as INT, FLOAT, DECIMAL, etc.
2. NULL Values: AVG() ignores NULL values in the calculation.
3. Grouping: It can be combined with the GROUP BY clause to calculate averages for groups of rows.

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Example 1: Simple Average

To calculate the average price of products:

SELECT AVG(Price) AS AveragePrice
FROM Products;

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Example 2: Using a Condition

To calculate the average price of products costing more than $50:

SELECT AVG(Price) AS AveragePrice
FROM Products
WHERE Price > 50;

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Example 3: Grouped Averages

To calculate the average price of products by category:

SELECT CategoryID, AVG(Price) AS AveragePrice
FROM Products
GROUP BY CategoryID;

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Example 4: Combining with Other Aggregate Functions

To calculate the total and average price of products:

SELECT SUM(Price) AS TotalPrice, AVG(Price) AS AveragePrice
FROM Products;

The AVG() function is straightforward and highly useful for summarizing numerical data in SQL queries.