The COUNT_DISTINCT function counts the number of unique items in a field.
Syntax
Parameters
X- a field or expression that contains the items to be counted.
How the COUNT_DISTINCT function works
The COUNT_DISTINCT function takes 1 parameter, which can be the name of a metric, dimension, or expression of any type. COUNT_DISTINCT returns the total number of unique items in that field or expression.
To count all items, including duplicates, use COUNT.
There are 2 other ways to apply this function:
- In a data source, change a field's Aggregation type to
Count Distinct. - in a report, edit the field's aggregation in a chart.
Examples
| Example formula | Output |
|---|---|
COUNT_DISTINCT(user_id) |
22,854,921 |
COUNT_DISTINCT(order_id) |
497,091,812 |
Limits of COUNT_DISTINCT
You can't apply this function to a pre-aggregated field (Aggregation type of Auto), or to an expression which is the result of another aggregation function. For example, a formula such as COUNT_DISTINCT(Sessions) in a Google Analytics data source will produce an error.
To avoid possibly incurring higher query costs when using BigQuery data sources, consider using APPROX_COUNT_DISTINCT.