Oracle 拆分字段为行，REGEXP_SUBSTR函数使用笔记记录

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查询SQL示例

with t as
 (select '312,564' str, 2 lvl from dual
  union all
  select '123,456,789' str, 3 lvl from dual
  )
select  REGEXP_SUBSTR(str ,'[^,]+', 1, level), lvl STR 
from (
     select str, lvl, rownum rn from t
) CONNECT BY level <= REGEXP_COUNT(str, ',') + 1 
  and rn = prior rn 
  and prior dbms_random.value is not null;

查询结果示例：

str	lvl
312	2
564	2
123	3
456	3
789	3

替代SQL示例：

with t as (
     select '123,456,789' str, 3 lvl from dual
     union all
     select '252,741' str, 2 lvl from dual
),
n(str, ori, pos, lvl) as (
       select distinct str || ',', 1, instr(str || ',', ','), lvl from t
       union all
       select str, pos + 1, instr(str, ',', pos + 1), lvl from n
       where instr(str, ',', pos + 1) > 0
)
select substr(str, ori, pos - ori) str, lvl from n;

查询结果示例：

str	lvl
123	3
252	2
456	3
741	2
789	3

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两种方式执行效率自行验证