# Aggregate Functions
Aggregate functions in SQL Server run calculations on sets of values, returning a single value.
# SUM()
Returns sum of numeric values in a given column.
We have table as shown in figure that will be used to perform different aggregate functions. The table name is Marksheet.
Select SUM(MarksObtained) From Marksheet
The sum function doesn't consider rows with NULL value in the field used as parameter
In the above example if we have another row like this:
106 Italian NULL
This row will not be consider in sum calculation
# AVG()
Returns average of numeric values in a given column.
We have table as shown in figure that will be used to perform different aggregate functions. The table name is Marksheet.
Select AVG(MarksObtained) From Marksheet
The average function doesn't consider rows with NULL value in the field used as parameter
In the above example if we have another row like this:
106 Italian NULL
This row will not be consider in average calculation
# MAX()
Returns the largest value in a given column.
We have table as shown in figure that will be used to perform different aggregate functions. The table name is Marksheet.
Select MAX(MarksObtained) From Marksheet
# MIN()
Returns the smallest value in a given column.
We have table as shown in figure that will be used to perform different aggregate functions. The table name is Marksheet.
Select MIN(MarksObtained) From Marksheet
# COUNT()
Returns the total number of values in a given column.
We have table as shown in figure that will be used to perform different aggregate functions. The table name is Marksheet.
Select COUNT(MarksObtained) From Marksheet
The count function doesn't consider rows with NULL value in the field used as parameter. Usually the count parameter is * (all fields) so only if all fields of row are NULLs this row will not be considered
In the above example if we have another row like this:
106 Italian NULL
This row will not be consider in count calculation
NOTE
The function COUNT(*) returns the number of rows in a table. This value can also be obtained by using a constant non-null expression that contains no column references, such as COUNT(1).
Example
Select COUNT(1) From Marksheet
# COUNT(Column_Name) with GROUP BY Column_Name
Most of the time we like to get the total number of occurrence of a column value in a table for example:
TABLE NAME : REPORTS
| ReportName | ReportPrice |
|---|---|
| Test | 10.00 $ |
| Test | 10.00 $ |
| Test | 10.00 $ |
| Test 2 | 11.00 $ |
| Test | 10.00 $ |
| Test 3 | 14.00 $ |
| Test 3 | 14.00 $ |
| Test 4 | 100.00 $ |
SELECT
ReportName AS REPORT NAME,
COUNT(ReportName) AS COUNT
FROM
REPORTS
GROUP BY
ReportName
| REPORT NAME | COUNT |
|---|---|
| Test | 4 |
| Test 2 | 1 |
| Test 3 | 2 |
| Test 4 | 1 |
# Syntax
- AVG([ALL|DISTINCT]expression)
- COUNT([ALL|DISTINCT]expression)
- MAX([ALL|DISTINCT]expression)
- MIN([ALL|DISTINCT]expression)
- SUM([ALL|DISTINCT]expression)