SQL 查询将具有多个状态更改日期列的单行转换为具有状态和时间戳的多行

Question

我的输入数据如下：

story_id || sched_state || story_being_groomed_ts || story_def_ts || story_in_prgrs_ts || story_cmpl_ts||

=========================================================================================================

1           completed      2023-01-01                2023-01-13      2023-01-20           2023-01-23

2           inprogress     2023-01-01                2023-01-10      2023-01-30

我希望我的输出是这样的：

根据时间戳可用性，共有 4 个阶段（已整理、定义、进行中和已完成），我们需要更新输出中的阶段。

story_id || sched_state  || last_up_ts

======================================

1          Groomed          2023-01-01

1          Defined          2023-01-13

1          inprogress       2023-01-20

1          Completed        2023-01-23

2          Groomed          2023-01-01

2          Defined          2023-01-10

2          inprogress       2023-01-30

你能帮我解决这个问题吗？

Answer 1

mysql 中没有直接的 unpivot 方法。可以按如下方式完成：

select story_id, sched_state, last_up_ts
from (
    select t.story_id,
      c.sched_state,
      case c.sched_state
        when 'Groomed' then story_being_groomed_ts
        when 'defined' then story_def_ts
        when 'inprogress' then story_in_prgrs_ts
        when 'completed' then story_cmpl_ts
      end as last_up_ts
    from mytable t
    cross join
    (
      select 'Groomed' as sched_state
      union all select 'defined'
      union all select 'inprogress'
      union all select 'completed'
    ) c
) sub
where last_up_ts is not null 
ORDER BY story_id, sched_state, last_up_ts