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Chapter 25: Functions (Aggregate)

Syntax

• Function([DISTINCT] expression) -DISTINCT is an optional parameter
• AVG ( [ ALL | DISTINCT ] expression )
• COUNT( { [ALL | DISTINCT ] expression ] | * } )
• GROUPING(<column_expression>)
• MAX ( [ ALL | DISTINCT ] expression )
• MIN ( [ ALL | DISTINCT ] expression )
• SUM ( [ ALL | DISTINCT ] expression )
• VAR ( [ ALL | DISTINCT ] expression )
OVER ( [ partition_by_clause ] order_by_clause )
• VARP ( [ ALL | DISTINCT ] expression )
OVER ( [ partition_by_clause ] order_by_clause
• STDEV ( [ ALL | DISTINCT ] expression )
OVER ( [ partition_by_clause ] order_by_clause )
• STDEVP ( [ ALL | DISTINCT ] expression )
OVER ( [ partition_by_clause ] order_by_clause )

Remarks

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
or measurement such as a set, a bag or a list.

MIN returns the smallest value in a given column
MAX returns the largest value in a given column
SUM returns the sum of the numeric values in a given column
AVG returns the average value of a given column
COUNT returns the total number of values in a given column
COUNT(*) returns the number of rows in a table
GROUPING Is a column or an expression that contains a column in a GROUP BY clause.
STDEV returns the statistical standard deviation of all values in the specified
expression.
STDEVP returns the statistical standard deviation for the population for all values in the
specified expression.
VAR returns the statistical variance of all values in the specified expression. may be
followed by the OVER clause.
VARP returns the statistical variance for the population for all values in the specified
expression.

Aggregate functions are used to compute against a "returned column of numeric data"
from your SELECT statement. They basically summarize the results of a particular
column of selected data. - SQLCourse2.com

All aggregate functions ignore NULL values.

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