Snowflake中argmin/argmax聚合的替代方案及OBJECT适配问题咨询

Great question! You're right that Snowflake doesn't support aggregating OBJECT types directly with MAX/MIN, unlike Hive's struct workaround. But there are a few clean ways to achieve the same argmin/argmax behavior in Snowflake—here are the most straightforward approaches:

1. Use Snowflake's Built-in MAX_BY/MIN_BY Functions #

Snowflake has dedicated functions for exactly this use case: MAX_BY(<return_value>, <sort_expression>) and MIN_BY(). These directly return the value from <return_value> that corresponds to the maximum/minimum value of <sort_expression>.

For your example (getting the x value where y is maximum), it's as simple as:

SELECT MAX_BY(x, y) FROM t;

If you need to return multiple columns tied to the max y, you can package them into an OBJECT or ARRAY first, then extract the fields you need:

-- Return the full object with x and other columns
SELECT MAX_BY(OBJECT_CONSTRUCT('x', x, 'other_col', other_col), y) FROM t;

-- Extract just the x value from the result
SELECT MAX_BY(OBJECT_CONSTRUCT('x', x, 'other_col', other_col), y):x FROM t;

2. Use Window Functions with QUALIFY #

If you need more flexibility (like retaining all rows that have the maximum y, not just one), window functions paired with Snowflake's QUALIFY clause work perfectly. This avoids needing a CTE for simpler queries:

-- Get all x values where y is maximum (use DENSE_RANK() to keep ties)
SELECT x
FROM t
QUALIFY DENSE_RANK() OVER (ORDER BY y DESC) = 1;

-- If you only want one row even with ties, use ROW_NUMBER() instead
SELECT x
FROM t
QUALIFY ROW_NUMBER() OVER (ORDER BY y DESC) = 1;

3. CTE + Window Function (Legacy/Compatible Approach) #

If you prefer using a CTE for clearer logic (or need compatibility with systems that don't support QUALIFY), you can define the ranking in a CTE first:

WITH ranked_rows AS (
    SELECT
        x,
        y,
        ROW_NUMBER() OVER (ORDER BY y DESC) AS rank_num
    FROM t
)
SELECT x FROM ranked_rows WHERE rank_num = 1;

Key Notes #

• MAX_BY/MIN_BY are the most concise and performant option for simple argmin/argmax use cases.
• Use DENSE_RANK() instead of ROW_NUMBER() if you want to include all rows that share the maximum/minimum y value.

内容的提问来源于stack exchange，提问作者Christoph Körner