Does Athena support ORDER BY in ARRAY_AGG ?

Question

It appears that Athena does not support ORDER BY within ARRAY_AGG function. Here is an example.

If I run the following query, it aggregates records into an array, as expected.

```
    WITH dataset AS (
       SELECT 1 AS breakdown_id, 1 AS history_order, 'OPEN' AS action
       UNION ALL
       SELECT 1 AS breakdown_id, 2 AS history_order, 'IN_PROGRESS' AS action
       UNION ALL
       SELECT 1 AS breakdown_id, 3 AS history_order, 'CLOSED' AS action
       UNION ALL
       SELECT 2 AS breakdown_id, 1 AS history_order, 'OPEN' AS action
       UNION ALL
       SELECT 2 AS breakdown_id, 2 AS history_order, 'IN_PROGRESS' AS action
       UNION ALL
       SELECT 3 AS breakdown_id, 1 AS history_order, 'OPEN' AS action
       UNION ALL
       SELECT 3 AS breakdown_id, 2 AS history_order, 'IN_PROGRESS' AS action
       UNION ALL
       SELECT 3 AS breakdown_id, 3 AS history_order, 'WAITING_FOR_INPUT' AS action
    
    )
    SELECT breakdown_id
         , ARRAY_AGG(action) AS actions
      FROM dataset
     GROUP BY breakdown_id
```

**Result:**

| #  | breakdown_id  | actions  |
|---|---|---|
| 1  | 1  | [IN_PROGRESS, CLOSED, OPEN]  |
| 2  | 2  | [WAITING_FOR_INPUT, IN_PROGRESS, OPEN]  |
| 3  | 2  | [IN_PROGRESS, OPEN]  |
 \
However the elements of the array need to be in the order specified by the history_order column. Unfortunately adding ORDER BY into the ARRAY_AGG function results in nothing being returned.

```
    WITH dataset AS (
       SELECT 1 AS breakdown_id, 1 AS history_order, 'OPEN' AS action
       UNION ALL
       SELECT 1 AS breakdown_id, 2 AS history_order, 'IN_PROGRESS' AS action
       UNION ALL
       SELECT 1 AS breakdown_id, 3 AS history_order, 'CLOSED' AS action
       UNION ALL
       SELECT 2 AS breakdown_id, 1 AS history_order, 'OPEN' AS action
       UNION ALL
       SELECT 2 AS breakdown_id, 2 AS history_order, 'IN_PROGRESS' AS action
       UNION ALL
       SELECT 3 AS breakdown_id, 1 AS history_order, 'OPEN' AS action
       UNION ALL
       SELECT 3 AS breakdown_id, 2 AS history_order, 'IN_PROGRESS' AS action
       UNION ALL
       SELECT 3 AS breakdown_id, 3 AS history_order, 'WAITING_FOR_INPUT' AS action
    
    )
    SELECT breakdown_id
         , ARRAY_AGG(action ORDER BY history_order) AS actions
      FROM dataset
     GROUP BY breakdown_id
```

**Result:**

| #  | breakdown_id  | actions  |
|---|---|---|
|   |   |  |

Is it a defect or a feature? And, more importantly, is there another way to get the array ordered by history_order?

Accepted Answer

Hi,

If you upgrade your Athena engine to v2, the query that was failing on you should work.

[https://docs.aws.amazon.com/athena/latest/ug/engine-versions-changing.html][1]

[1]: https://docs.aws.amazon.com/athena/latest/ug/engine-versions-changing.html

#	breakdown_id	actions
1	1	[IN_PROGRESS, CLOSED, OPEN]
2	2	[WAITING_FOR_INPUT, IN_PROGRESS, OPEN]
3	2	[IN_PROGRESS, OPEN]
\
However the elements of the array need to be in the order specified by the history_order column. Unfortunately adding ORDER BY into the ARRAY_AGG function results in nothing being returned.

Does Athena support ORDER BY in ARRAY_AGG ?

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