Amazon Athena
User Guide

Accessing Array Elements

To access array elements, use the [] operator, with 1 specifying the first element, 2 specifying the second element, and so on, as in this example:

WITH dataset AS ( SELECT ARRAY[CAST(MAP(ARRAY['a1', 'a2', 'a3'], ARRAY[1, 2, 3]) AS JSON)] || ARRAY[CAST(MAP(ARRAY['b1', 'b2', 'b3'], ARRAY[4, 5, 6]) AS JSON)] AS items ) SELECT items[1] AS item FROM dataset

This query returns:

+------------------------+ | item | +------------------------+ | {"a1":1,"a2":2,"a3":3} | +------------------------+

To access the elements of an array at a given position (known as the index position), use the element_at() function and specify the array name and the index position:

  • If the index is greater than 0, element_at() returns the element that you specify, counting from the beginning to the end of the array. It behaves as the [] operator.

  • If the index is less than 0, element_at() returns the element counting from the end to the beginning of the array.

The following query creates an array words, and selects the first element hello from it as the first_word, the second element amazon (counting from the end of the array) as the middle_word, and the third element athena, as the last_word.

WITH dataset AS ( SELECT ARRAY ['hello', 'amazon', 'athena'] AS words ) SELECT element_at(words, 1) AS first_word, element_at(words, -2) AS middle_word, element_at(words, cardinality(words)) AS last_word FROM dataset

This query returns:

+----------------------------------------+ | first_word | middle_word | last_word | +----------------------------------------+ | hello | amazon | athena | +----------------------------------------+