What are the aggregate functions in SQL server?

What are the aggregate functions in SQL server?

Count, Min, Max and Average are the few aggregate functions in SQL Server.

Count function:  Select count (*) from Table1.  It will deliver count of the table i.e. no of records. If you will put the filters in the query then it will give the count of filtered records.

table Employee as designed below.

             

Name	Age	Salary	Total No of CARS
Randheer	19	10000	1
Nids	17	50000	2
Jayant		null	3
Ruby	5	2000	0

Case 1

Question.  Select  Count (Salary) from Employee?

A)    4  B)0 C)3 D) 2

Answer: In this case answer will be C as the null values in a column doesn’t counts by the count function in SQL Server.

Case 2

Question.  Select  Count (Age) from Employee?

A)    4  B)0 C)3 D) 2

Answer: In this case answer will be A as the space will be consider as a value by count function in SQL Server.

Min function: Min function retrieves the minimum values in a column it works on group by function and also without any group by function.

select min(salary) from(select 1 as ID, 'Randheer' as Name,'10000' as salaryunion allselect 1 as ID, 'Randheer' as Name,null as salaryunion allselect 1 as ID, 'Randheer' as Name,'80000' as salary)

Result will 10000 in  this case. it shows that min function is not considering the null value.
 Max Function: Max function is used to get the max value of a column.
A

Select Max (column1) from table1

Average Function: Average is used to get the average of the column. Average can be on the groups also. This functions returns value as mathematics average function returns.