Using the built-in User-defined Aggregation Function (UDAF)

Hive provides a set of functions to do aggregation on a dataset. These functions operate on a range of data (rows) and provide the cumulative or relative result.

How to do it…

The built-in functions could be used directly in the query. The following are some of the examples of aggregated functions available in Hive:

Function Name	Return Type	Description
avg(col)	DOUBLE	It is used to calculate the average of all values of a particular column.
avg(DISTINCT col)	DOUBLE	It is used to calculate the average of unique values of a particular column.
collect_list(col)	ARRAY	It will return a list of all values of a particular column in an array.
collect_set(col)	ARRAY	It will return a list of unique values of a particular column in an array. Duplicate values are eliminated.
corr(col1, col2)	DOUBLE	It is used to calculate the Pearson coefficient of correlation between two columns.
count(*)	BIGINT	It will return the total...