(HANA SQL) 在一行中显示多个值

Question

我正在尝试完成以下内容：

旧情况

我想要什么

Answer 1

对于固定的最大目标列数，可以使用窗口函数和条件聚合：

select customer,
    max(case when rn = 1 then order_date end) as order_date_1,
    max(case when rn = 2 then order_date end) as order_date_2,
    max(case when rn = 3 then order_date end) as order_date_3
from (
    select t.*, row_number() over(partition by customer order by order_date) rn
    from mytable t
) t
group by customer