如何消除列中的重复数据

Question

我想消除重复并显示一次

例如

SELECT 'apple, apple, orange'
FROM dual;

我想展示

apple, orange

作为另一个例子。

SELECT 'apple, apple, apple, apple,'
FROM dual;

我只想展示

apple

这段代码显示

with data as
(
  select 'apple, apple, apple, apple' col from dual
)
select listagg(col, ',') within group(order by 1) col
  from (
        select distinct regexp_substr(col, '[^,]+', 1, level) col
          from data
        connect by level <= regexp_count(col, ',')
       )

Answer 1

这样的事情会消除重复：

SQL Demo

with temp as
(
    select 1 Name, 'test1' Project, 'apple, apple, orange' Error  from dual
    union all
    select 2, 'test2', 'apple, apple, apple, apple,' from dual
), split as (
    select distinct
      t.name, t.project,
      trim(regexp_substr(t.error, '[^,]+', 1, levels.column_value))  as error
    from 
      temp t,
      table(cast(multiset(select level 
                          from dual connect by  level <= length (regexp_replace(t.error, '[^,]+'))  + 1) as sys.OdciNumberList)) levels
)
SELECT Name, listagg(Error, ',') within group(order by 1) as result 
FROM split
GROUP BY Name

输出

如您所见，您得到一个 NULL，因为额外的逗号 ,

Answer 2

Oracle forum 中有几个选项：

with data as
 (
 select 

'5,5,5,5,6,6,5,5,5,6,7,4,1,2,1,4,7,2' col from dual
)
 select listagg(col, ',') within group(order by 1) col
 from (
    select distinct regexp_substr(col, '[^,]+', 1, level) col
    from data
    connect by level <= regexp_count(col, ',')
   )

只需将数字替换为'apple, apple, orange'

Answer 3

将trim 和distinct 与regexp 函数一起使用对于获得所需的结果非常重要

select listagg(str,',') within group (order by 0) as Result
from
(
 select distinct trim(regexp_substr('apple, apple, orange','[^,]+', 1, level)) as str
   from dual
connect by level <= regexp_count('apple, apple, orange',',') + 1
);

Rextester Demo