Question

我在运行此查询时“错过了右括号错误”

select a.session_id,
       a.request_id,
       a.timestamp,
       a.queue_tag,
       b.*
  from (select session_id,
               request_id,
               timestamp,
               queue_tag,
               (select min(b.timestamp) nextrec
                  from tbl b
                 where a.session_id = b.session_id
                   and a.request_id = b.request_id
                   and b.timestamp > a.timestamp
                   and b.is_queue_empty = 0
               )
          from tbl a
         where is_queue_empty = 1 
            and nullif(queue_name,'') is null
       ) a
       left join tbl b 
    on a.session_id = b.session_id
   and a.request_id = b.request_id
   and a.nextrec = b.timestamp

在Oracle中选择这样的列值是否有效？如果不是我在这里缺少的东西？

Answer 1

我上面的查询工作，不得不移出列别名（由@Martin建议）并删除多余的nullIf（）

with tbl as(
            select SYSTIMESTAMP+1 timestamp, 0 is_queue_empty , '' queue_name , 'qt' queue_tag, -1 session_id , 1 request_id from dual
            union all
            select SYSTIMESTAMP timestamp, 1 is_queue_empty , '' queue_name , 'qt1' queue_tag, -1 session_id , 1 request_id from dual
            union all
            select SYSTIMESTAMP+1 timestamp, 0 is_queue_empty , '' queue_name , 'qt2' queue_tag, -2 session_id , 2 request_id from dual
            union all
            select SYSTIMESTAMP timestamp,  1 is_queue_empty , '' queue_name , 'qt22' queue_tag, -2 session_id , 2 request_id from dual            
)
select a.session_id,a.request_id,a.timestamp,a.queue_tag,
  b.*
from
(
    select session_id,request_id,timestamp,queue_tag,
     (select min(b.timestamp) nextrec
      from tbl b
      where a.session_id=b.session_id
        and a.request_id=b.request_id
        and b.timestamp > a.timestamp
        and b.is_queue_empty=0) nextrec --> had to put this outside the loop
    from tbl a
    where is_queue_empty=1 and queue_name is null --in oracle empty string is null thus nullif(queue_name,'') is redundant
) a
left join tbl b on a.session_id=b.session_id
               and a.request_id=b.request_id
               and a.nextrec = b.timestamp

Answer 2

您只需在标量子查询后添加别名nextrec。您在该查询中命名，但是当在左连接中加入时，Oracle不知道它的列名。这应该有效：

select a.session_id,
       a.request_id,
       a.timestamp,
       a.queue_tag,
       b.*
  from (select session_id,
               request_id,
               timestamp,
               queue_tag,
               (select min(b.timestamp) nextrec
                  from tbl b
                 where a.session_id = b.session_id
                   and a.request_id = b.request_id
                   and b.timestamp > a.timestamp
                   and b.is_queue_empty = 0
               ) nextrec
          from tbl a
         where is_queue_empty = 1 
            and nullif(queue_name,'') is null
       ) a
       left join tbl b 
    on a.session_id = b.session_id
   and a.request_id = b.request_id
   and a.nextrec = b.timestamp

此外，当我在Oracle 10g上运行您的原始查询时，我从数据库中收到以下更具描述性的错误：

and a.nextrec = b.timestamp
           *
ERROR at line 44:
ORA-00904: "A"."NEXTREC": invalid identifier

帮助Oracle查询（缺少右括号）

2 个答案: