Question

我正在寻找一个可以从多个表中获取多个字段并将它们合并到一个字段中的查询。防爆。我的查询看起来像：

select to_char(a.comments), to_char(b.comments), to_char(c.comments)
from      crm.custprob a
left join crm.custcall b on b.servno = a.servno
left join crm.custlog c on c.servno = b.servno
where a.servno = 1716942

并生成输出：

a.comments   b.comments    c.comments
1 Regular    3 Primary     5 Log
1 Regular    3 Primary     4 Log
1 Regular    2 Other       5 Log
1 Regular    2 Other       4 Log

我想要的是一个查询，它会在一行中生成输出，并在一个字段中（我不关心数字的顺序）所以它看起来像：

Comments
1 Regular 2 Other 3 Primary 4 Log 5 Log

Answer 1

首先获取所有评论的列表。您将UNION用于此，而不是加入。然后使用LISTAGG聚合行并连接注释：

select listagg(comments, ' ') within group (order by comments) as comments
from
(
  select to_char(comments) as comments from crm.custprob where servno = 1716942
  union
  select to_char(comments) as comments from crm.custcall where servno = 1716942
  union
  select to_char(comments) as comments from crm.custlog where servno = 1716942
);

（如果没有重复项，您可以使用UNION ALL代替UNION。）

（根据以下评论进行了更新，其中显示comments属于NCLOB类型。）

Answer 2

这是在加入之前对各个表执行listagg的替代方法：

WITH t1 AS (SELECT 1 ID, '1 regular' comments FROM dual UNION ALL
            SELECT 2 ID, '1 abnormal' comments FROM dual),
     t2 AS (SELECT 1 ID, '2 other' comments FROM dual UNION ALL
            SELECT 1 ID, '3 primary' comments FROM dual UNION ALL
            SELECT 2 ID, '2 something else' comments FROM dual UNION ALL
            SELECT 2 ID, '3 secondary' comments FROM dual),
     t3 AS (SELECT 1 ID, '4 log' comments FROM dual UNION ALL
            SELECT 1 ID, '5 log' comments FROM dual UNION ALL
            SELECT 2 ID, '4 log' comments FROM dual UNION ALL
            SELECT 2 ID, '5 log' comments FROM dual)
SELECT t1.id,
       t1.comments||' '||t_2.comments||' '||t_3.comments comments
FROM   t1
       LEFT OUTER JOIN (SELECT ID, listagg(comments, ' ') WITHIN GROUP (ORDER BY comments) comments
                        FROM   t2
                        GROUP BY ID) t_2 ON t1.id = t_2.id
       LEFT OUTER JOIN (SELECT ID, listagg(comments, ' ') WITHIN GROUP (ORDER BY comments) comments
                        FROM   t3
                        GROUP BY ID) t_3 ON t_2.id = t_3.id;

        ID COMMENTS
---------- --------------------------------------------------------------------------------
         1 1 regular 2 other 3 primary 4 log 5 log
         2 1 abnormal 2 something else 3 secondary 4 log 5 log

Answer 3

这有用吗？

select listagg(comments, ' ') within group (order by ordering) as comments
from (select comments from crm.custprob, 1 as ordering where servno = 1716942
      union all
      select comments from crm.custcall, 2 where servno = 1716942
      union all
      select comments from crm.custlog, 3 where servno = 1716942
     ) x;

Oracle - 从多个表到一个字段的多行

3 个答案: