技术咨询：如何基于每组的ROW_NUMBER实现分组？

Hey there! Since you mentioned needing to group your data using ROW_NUMBER() and referenced an attached image with details, I’ll walk through the most common use cases for this requirement—these should align with typical scenarios where you’d need this logic.

Common Scenarios & Solutions #

1. Group Rows into Fixed-Sized Batches #

If you want to split your data into groups of a specific number of rows (e.g., every 3 rows as one group), you can use arithmetic on the ROW_NUMBER() result to generate a consistent group ID:

SELECT
  -- Include your existing table columns here
  customer_id,
  order_date,
  order_amount,
  -- Generate a unique row number sorted by your target column
  ROW_NUMBER() OVER (ORDER BY order_date) AS row_num,
  -- Split rows into batches of 3; adjust the number to fit your needs
  FLOOR((ROW_NUMBER() OVER (ORDER BY order_date) - 1) / 3) AS group_id
FROM orders;

• The -1 ensures our first group starts at 0 (remove it if you prefer groups to start counting from 1).
• Swap 3 with your desired group size, and order_date with the column you want to sort rows by before grouping.

2. Group Consecutive Rows Within Partitions #

If you’re using PARTITION BY in your ROW_NUMBER() (e.g., numbering rows per customer) and want to group consecutive rows within each partition, combine ROW_NUMBER() with another window function to create a stable grouping key:

WITH numbered_rows AS (
  SELECT
    customer_id,
    order_date,
    order_amount,
    -- Number rows per customer, sorted by order date
    ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY order_date) AS row_num
  FROM orders
)
SELECT
  *,
  -- Creates a fixed group ID for consecutive rows in each customer's partition
  row_num - ROW_NUMBER() OVER (PARTITION BY customer_id ORDER BY row_num) AS group_id
FROM numbered_rows;

This trick works because the difference between the two row numbers stays identical for consecutive rows in the same partition.

Need a More Tailored Fix? #

If your specific use case (like grouping based on a condition tied to ROW_NUMBER(), or using a database like PostgreSQL/SQL Server with unique syntax) doesn’t match these examples, share a bit more detail:

• The structure of your source table
• The exact grouping rule you need (e.g., "group every time the row number resets" or "group odd/even row numbers separately")
• A sample of your desired output

That way I can refine this to fit your exact scenario!

内容的提问来源于stack exchange，提问作者Sai Prasad