COUNT

Counts the number of rows or not NULL values.

Syntax

COUNT([ DISTINCT ] <expression>)

Parameters

Valid values for the input expression include column names or functions that return a column name. When DISTINCT is being used, only the unique number of rows with no NULL values are counted. COUNT(*) returns a total count of all rows in the table, while COUNT(<column_name>) returns a count of non-null rows in the specified <column_name>.

By default, COUNT(DISTINCT) returns approximate results. If you require a precise result (with a performance penalty), please contact Firebolt Support through the Help menu support form.

Return Types

NUMERIC

Example

For this example, see the following table tournaments:

Doing a regular COUNT returns the total number of rows in the column. As the tournaments table contains 6 rows, this will be the returned value.

SELECT
	COUNT(name)
FROM
	tournaments;

Returns: 6

A COUNT(DISTINCT) function on the same column returns the number of unique rows. When applied to the totalprizedollars column, the value returned is 5, as there is a repeated number in the column.

SELECT
	COUNT(DISTINCT totalprizedollars)
FROM
	tournaments;

Returns: 5

Example of COUNT(DISTINCT) vs. APPROX_COUNT_DISTINCT

To understand the difference between COUNT(DISTINCT pk) with exact precision enabled and using default approximation, consider a table, count_test with 8,388,608 unique pk values. The APPROX_COUNT_DISTINCT function returns the same approximate results as the COUNT(DISTINCT) function with exact precision disabled, so we can see the difference between these methods with the following example.

SELECT
	COUNT(DISTINCT pk) as count_distinct,
	APPROX_COUNT_DISTINCT(pk) as approx_count
FROM
	count_test;

Returns:

Assuming 8,388,608 unique pk values, we will see results like:

' +----------------+--------------+
' | count_distinct | approx_count |
' +----------------+--------------+
' |      8,388,608 |    8,427,387 |
' +----------------+--------------+