TOPN_WEIGHTED

Description

The TOPN_WEIGHTED function returns the N most frequent values in the specified column with weighted counting. Unlike the regular TOPN function, TOPN_WEIGHTED allows adjusting the importance of values through weights.

Syntax

TOPN_WEIGHTED(<expr>, <weight>, <top_num> [, <space_expand_rate>])

Parameters

Parameter	Description
<expr>	The column or expression to be counted
<weight>	The column or expression to adjust the weight
<top_num>	The number of the most frequent values to return. It must be a positive integer.
<space_expand_rate>	Optional, the value to set the counter_numbers used in the Space-Saving algorithm. counter_numbers = top_num * space_expand_rate. The value of space_expand_rate should be greater than 1, and the default value is 50.

Return Value

Return an array containing values and weighted counts.

Examples

-- create example table
CREATE TABLE product_sales (
    product_id INT,
    sale_amount DECIMAL(10,2),
    sale_date DATE
) DISTRIBUTED BY HASH(product_id)
PROPERTIES (
    "replication_num" = "1"
);

-- insert test data
INSERT INTO product_sales VALUES
(1, 100.00, '2024-01-01'),
(2, 50.00, '2024-01-01'),
(1, 150.00, '2024-01-01'),
(3, 75.00, '2024-01-01'),
(1, 200.00, '2024-01-01'),
(2, 80.00, '2024-01-01'),
(1, 120.00, '2024-01-01'),
(4, 90.00, '2024-01-01');

-- find the top 3 products with highest sales amount
SELECT TOPN_WEIGHTED(product_id, sale_amount, 3) as top_products
FROM product_sales;

+--------------+
| top_products |
+--------------+
| [1, 2, 4]    |
+--------------+