Question

我有一个员工数据库，其中包含有关员工的记录。字段是：

employee_identifier
employee_salary
date_of_the_record

我想为每条记录获取employee_salary中最后一次更改的日期。哪个SQL查询可以工作？

我尝试了多个子查询，但是它不起作用。

Answer 1

以下是用于BigQuery标准SQL

#standardSQL
SELECT * EXCEPT(arr),
  (SELECT MAX(date_of_the_record) FROM UNNEST(arr)
    WHERE employee_salary != t.employee_salary
  ) AS last_change_in_employee_salary
FROM (
  SELECT *, ARRAY_AGG(STRUCT(employee_salary, date_of_the_record)) OVER(win) arr
  FROM `project.dataset.employee_database`
  WINDOW win AS (PARTITION BY employee_identifier ORDER BY date_of_the_record)
) t

Answer 2

使用row_number()

with cte as
(
select *,
row_number()over(partition by employee_identifier order by date_of_the_record desc) rn from table_name
) select * from cte where rn=1

Answer 3

您也可以在没有子查询的情况下执行此操作。如果要所有列：

SELECT as value ARRAY_AGG(t ORDER BY date_of_the_record DESC LIMIT 1)[ordinal(1)]
FROM t t
GROUP BY employee_identifier;

如果只需要日期，请使用GROUP BY：

SELECT employee_identifier, MAX(date_of_the_record)
FROM t t
GROUP BY employee_identifier;

获取Google BigQuery中值最后一次更改的时间

3 个答案: