COUNT_DISTINCT

Aggregate function.

The count(distinct ...) function calculates the uniq value of a set of values.

To obtain an estimated result from large data sets with little memory and time, consider using APPROX_COUNT_DISTINCT.

caution

NULL values are not counted.

Syntax

COUNT(distinct <expr> ...)
UNIQ(<expr>)

Arguments

Arguments	Description
<expr>	Any expression, size of the arguments is [1, 32]

Return Type

UInt64

Example

Create a Table and Insert Sample Data

CREATE TABLE products (
  id INT,
  name VARCHAR,
  category VARCHAR,
  price FLOAT
);

INSERT INTO products (id, name, category, price)
VALUES (1, 'Laptop', 'Electronics', 1000),
       (2, 'Smartphone', 'Electronics', 800),
       (3, 'Tablet', 'Electronics', 600),
       (4, 'Chair', 'Furniture', 150),
       (5, 'Table', 'Furniture', 300);

Query Demo: Count Distinct Categories

SELECT COUNT(DISTINCT category) AS unique_categories
FROM products;

Result

| unique_categories |
|-------------------|
|         2         |