Use aggregation functions with arrays - Amazon Athena
Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Use aggregation functions with arrays

  • To add values within an array, use SUM, as in the following example.

  • To aggregate multiple rows within an array, use array_agg. For information, see Create arrays from subqueries.

Note

ORDER BY is supported for aggregation functions starting in Athena engine version 2.

WITH dataset AS ( SELECT ARRAY [ ARRAY[1,2,3,4], ARRAY[5,6,7,8], ARRAY[9,0] ] AS items ), item AS ( SELECT i AS array_items FROM dataset, UNNEST(items) AS t(i) ) SELECT array_items, sum(val) AS total FROM item, UNNEST(array_items) AS t(val) GROUP BY array_items;

In the last SELECT statement, instead of using sum() and UNNEST, you can use reduce() to decrease processing time and data transfer, as in the following example.

WITH dataset AS ( SELECT ARRAY [ ARRAY[1,2,3,4], ARRAY[5,6,7,8], ARRAY[9,0] ] AS items ), item AS ( SELECT i AS array_items FROM dataset, UNNEST(items) AS t(i) ) SELECT array_items, reduce(array_items, 0 , (s, x) -> s + x, s -> s) AS total FROM item;

Either query returns the following results. The order of returned results is not guaranteed.

+----------------------+ | array_items | total | +----------------------+ | [1, 2, 3, 4] | 10 | | [5, 6, 7, 8] | 26 | | [9, 0] | 9 | +----------------------+