The approximate number of distinct values in the time window.
Use this function instead of COUNT_DISTINCT to improve performance. This should be used when there are relatively few (under 1 million) rows, and where the total number of distinct values is high.
Syntax
APPROX_COUNT_DISTINCT(VALUE)
Arguments
VALUE: Can be of any type
Returns
An integer.
Notes
Duplicate rows are not counted.
NULLs are not counted.
Count the number of distinct entries for each unique entry in a field:
SET
DATE_TIME = TO_DATE(data.CONNECTION_TIME);
SELECT
APPROX_COUNT_DISTINCT(data.USER_ID)
AS approx_count_distinct_data_user_id:BIGINT,
data.GROUP_ID AS group_id:STRING
FROM
"SAMPLE_DATA_G1U1 - json"
GROUP BY
data.GROUP_ID
