AWS Athena max 函数如何处理 Null 值

Question

I have a table in AWS Athena with a column that contains NULL values.

I want to calculate the max value for this column.

How would Athena calculate max value for a column that contains both Nulls and non-Nulls?

For the following example:

What would be the output for the following query:

select max(uploaded_mb) from table_name;

Answer 1

The Presto max() function returns the maximum value of all input values. Nulls won't affect that.

Here's an example query that shows that NULLs are ignored:

WITH
  t1 AS (SELECT 1 AS a),
  t2 AS (SELECT NULL AS a),
  tf AS (
    SELECT * FROM t1
    UNION ALL 
    SELECT * FROM t2
  )
SELECT max(a)
FROM tf

Did you get an error or see unexpected behaviour when using max() ?