# Aggregate functions in SQL

In database management an aggregate function is a function where the values of multiple rows are grouped together as input on certain criteria to form a single value of more significant meaning.

**Various Aggregate Functions**

1) Count() 2) Sum() 3) Avg() 4) Min() 5) Max()

Now let us understand each Aggregate function with a example:

Id Name Salary ----------------------- 1 A 80 2 B 40 3 C 60 4 D 70 5 E 60 6 F Null

**Count():**

* Count(*):* Returns total number of records .i.e 6.

*Return number of Non Null values over the column salary. i.e 5.*

**Count(salary):***Return number of distinct Non Null values over the column salary .i.e 4*

**Count(Distinct Salary):**

**Sum():**

* sum(salary): * Sum all Non Null values of Column salary i.e., 310

*Sum of all distinct Non-Null values i.e., 250.*

**sum(Distinct salary):**

**Avg():**

* Avg(salary)* = Sum(salary) / count(salary) = 310/5

*= sum(Distinct salary) / Count(Distinct Salary) = 250/4*

**Avg(Distinct salary)**

**Min():**

* Min(salary): *Minimum value in the salary column except NULL i.e., 40.

*Maximum value in the salary i.e., 80.*

**Max(salary):**

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