ROW_NUMBER() OVER PARTITON BY Syntax in Bigquery

Use the ROW_NUMBER() over analytic functions to Calculate ROW_NUMBER. Analytic functions are evaluated after aggregation (GROUP BY and non-analytic aggregate functions)

The following query finds the early employee in each department:

SELECT firstname, department, startdate,
  ROW_NUMBER() OVER ( PARTITION BY department ORDER BY startdate ) AS rank
FROM Employees;

you can extend this query to only see the top users,

Select A.* from (
SELECT firstname, department, startdate,
  ROW_NUMBER() OVER ( PARTITION BY department ORDER BY startdate ) AS rownum
FROM Employees)A
where A.rownum=1;

nVector

posted on 20 Sep 19