Aggregate Functions

An aggregate function is a function that takes in multiple values and returns a single value. It can be viewed as a function that performs an operation over the values of multiple rows.

In T-SQL, we have these aggregate functions:

• AVG(): Returns the average of supplied values
• COUNT(): Returns the number of rows
• MIN(): Returns the minimum value
• MAX(): Returns the maximum value
• SUM(): Returns the sum

As an argument, all aggregate functions take an expression that returns a range of values. Often, the expression is the name of the column over the values of which we want to perform the operation:

SELECT

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