postgresql - postgres 从 regexp_split_to_table 生成的行中选择并抛出错误的位置

Question

我有一个表“my_table”，其中有两列 (c1,c2) 以完全相同的格式保存数据“1,2,3,4;5,6,7,8” 我使用 regexp_split_to_table 将它们拆分成行，并尝试选择非空行。

SELECT * from 
 (SELECT '1' as param1 ,'2' as param2, param3 FROM
  ((select regexp_split_to_table(my_table.c1, ';') as param3
   FROM  my_table)
 UNION
  (select regexp_split_to_table(my_table.c2, ';') as param3
   FROM  my_table)) AS a) as b

 where param3 is not null

运行此查询会出现以下错误:

set-valued function called in context that cannot accept a set

如果我删除并集并仅从其中一列中进行选择，或者按其他字段之一 (param1/param2) 进行过滤，则查询有效。 我认为这可能是数据的问题，所以我尝试从同一列中选择两次:

SELECT * from 
 (SELECT '1' as param1 ,'2' as param2, param3 FROM
  ((select regexp_split_to_table(my_table.c1, ';') as param3
   FROM  my_table)
 UNION
  (select regexp_split_to_table(my_table.c1, ';') as param3
   FROM  my_table)) AS a) as b

 where param3 is not null

但我仍然得到同样的错误。 有人知道如何解决这个问题吗？ 谢谢!

Answer 1

我建议使用 CTE 而不是子查询并格式化您的查询。这是我认为您需要的查询:

with cte1 as (
  select regexp_split_to_table(t.c1, ';') as param3
  from my_table as t
  union all
  select regexp_split_to_table(t.c2, ';') as param3
  from my_table as t
)
select '1' as param1 ,'2' as param2, c.param3
from cte1 as c
where c.param3 is not null

sql fiddle demo

注意:我不知道您的查询是否需要重复项，所以如果您不需要 - 使用 union 而不是 union all

更新

with cte1 as (
  select regexp_split_to_table(t.c1, ';') as param3
  from my_table as t
  union all
  select regexp_split_to_table(t.c2, ';') as param3
  from my_table as t
), cte2 as (
  select regexp_split_to_table(c.param3, ',') as param3
  from cte1 as c
  where c.param3 is not null and c.param3 <> ''
)
select *
from cte2 as c
where c.param3 is not null and c.param3 <> ''

sql fiddle demo

update2 甚至可以用一个正则表达式来完成

with cte1 as (
    select c1 as param3 from my_table
    union all
    select c2 as param3 from my_table
), cte2 as (
  select regexp_split_to_table(param3, '(;|,)') as param3
  from cte1
)
select '1' as param1 ,'2' as param2, c.param3
from cte2 as c
where nullif(c.param3, '') <> ''

sql fiddle demo