sql - 合并查询返回 ORA-30926 : unable to get a stable set of rows in the source tables

Question

我有两个合并查询一个接一个地触发

第一次查询

merge into MyTable
using
(   
select distinct nullLogSetId.Id as IdToUpdate,
       knownLogSetId.LogSetId LogSetIdToUpdateTo
from MyTable knownLogSetId 
join MyTable nullLogSetId
  on knownLogSetId.IdentifierType = nullLogSetId.IdentifierType
 and knownLogSetId.Identifier = nullLogSetId.Identifier 
where 

    knownLogSetId.IdentifierType = 'ABC'
    and knownLogSetId.LogSetId >= 0 
    and nullLogSetId.LogSetId = -1
)
on (Id = IdToUpdate)
when matched then
update set LogSetId = LogSetIdToUpdateTo

第二次查询

merge into MyTable
using
(

  select distinct nullLogSetId.Id as IdToUpdate,
                  knownLogSetId.LogSetId LogSetIdToUpdateTo
  from MyTable knownLogSetId 
  join MyTable nullLogSetId
    on knownLogSetId.IdentifierType = nullLogSetId.IdentifierType 
   and knownLogSetId.Identifier = nullLogSetId.Identifier 
  where 
    knownLogSetId.IdentifierType = 'DEF'
    and knownLogSetId.LogSetId >= 0 
    and nullLogSetId.LogSetId = -1
) on (Id = IdToUpdate)
when matched then
update set LogSetId = LogSetIdToUpdateTo

我使用 OracleCommand 一个接一个地从 .NET 调用这些查询

第一个工作正常，但是当第二个被触发时，我得到了错误

ORA-30926: unable to get a stable set of rows in the source tables

我已经阅读了所有相关问题，并从我这边尝试过，如果您发现我在两个查询中都使用了 distinct，那么重复行不是问题。可以请任何人帮助我我做错了什么，这可能是一个基本的东西，因为我是新的查询，请帮助我

Answer 1

if you see i used distinct in both of the queries so duplicating of rows is not an issue.

您可能在数据中有重复项。 DISTINCT 不保证您的 IdToUpdate 与其他列一起使用时是唯一的。 请参阅:

CREATE TABLE #MyTable(IdToUpdate INT, LogSetIdToUpdateTo INT);

INSERT INTO #MyTable VALUES (1,1), (1,2), (2,1),(3,1);

SELECT DISTINCT IdToUpdate, LogSetIdToUpdateTo
FROM #MyTable;

LiveDemo

您将获得 IdToUpdate 两次。检查您的数据:

with cte AS (
  select distinct nullLogSetId.Id as IdToUpdate,
                  knownLogSetId.LogSetId LogSetIdToUpdateTo
  from MyTable knownLogSetId 
  join MyTable nullLogSetId
    on knownLogSetId.IdentifierType = nullLogSetId.IdentifierType 
   and knownLogSetId.Identifier = nullLogSetId.Identifier 
  where 
    knownLogSetId.IdentifierType = 'DEF'
    and knownLogSetId.LogSetId >= 0 
    and nullLogSetId.LogSetId = -1
)
SELECT IdToUpdate, COUNT(*) AS c
FROM cte
GROUP BY IdToUpdate
HAVING COUNT(*) > 1;

一种方法是使用聚合函数(MAX/MIN) 而不是DISTINCT:

merge into MyTable
using
(

  select nullLogSetId.Id as IdToUpdate,
         MAX(knownLogSetId.LogSetId) AS LogSetIdToUpdateTo 
  from MyTable knownLogSetId 
  join MyTable nullLogSetId
    on knownLogSetId.IdentifierType = nullLogSetId.IdentifierType 
   and knownLogSetId.Identifier = nullLogSetId.Identifier 
  where 
    knownLogSetId.IdentifierType = 'DEF'
    and knownLogSetId.LogSetId >= 0 
    and nullLogSetId.LogSetId = -1
  GROUP BY nullLogSetId.Id
) on (Id = IdToUpdate)
when matched then
update set LogSetId = LogSetIdToUpdateTo