TOPN_WEIGHTED
Descriptionβ
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.
Syntaxβ
TOPN_WEIGHTED(<expr>, <weight>, <top_num> [, <space_expand_rate>])
Parametersβ
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 Valueβ
Return an array containing values and weighted counts.
Examplesβ
-- 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] |
+--------------+