Oracle SQL：根据行重新启动序列

Question

我的数据集如下：

**series**
start
continue
continue
end
start
continue
end

我需要添加一个包含序列 ('leeftijd_seq') 的列，该序列从 'start' 开始，在 'continue' 增加 1，在 'end' 结束。我试过下面的代码，但我的执行语句对我创建的序列不起作用。

SELECT batchnr, series,
  CASE WHEN series = 'start' THEN execute 'alter sequence leeftijd_seq restart start with 1;' and leeftijd_seq.nextval
    when series = 'continue' then leeftijd_seq.nextval
    ELSE leeftijd_seq.currval
    END SEQ_NO
FROM data order by batchnr asc

Answer 1

这看起来像是一个缺口和孤岛问题。我建议使用 window 个“start”来构建组：

select t.*,
    row_number() over(partition by grp order by batchnr) as seq_no
from (
    select t.*,
        sum(case when series = 'start' then 1 else 0 end) over(order by batchnr) as grp
    from mytable t
) t

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