openquery 给出不同的结果
我有 2 个类似的查询
select *
from openquery(powerschool,
'select *
from TEACHERS
where teachernumber is not null
and schoolid=''1050''
and teacherloginid is not null
order by teachernumber')
，
SELECT *
from openquery(powerschool,
'SELECT NVL(teachernumber,'''')
from TEACHERS
where teachernumber is not null
and schoolid=''1050''
and teacherloginid is not null
order by teachernumber')
第一个查询给了我 182 行，而第二个查询给了我 83 行。
查询有什么问题？
I have 2 similar queries
select *
from openquery(powerschool,
'select *
from TEACHERS
where teachernumber is not null
and schoolid=''1050''
and teacherloginid is not null
order by teachernumber')
and
SELECT *
from openquery(powerschool,
'SELECT NVL(teachernumber,'''')
from TEACHERS
where teachernumber is not null
and schoolid=''1050''
and teacherloginid is not null
order by teachernumber')
The first one is giving me 182 rows while the second one gives me 83.
What's wrong with the queries?
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评论（2）
只是想法...
同一服务器？ 也就是说，链接服务器的目标或凭据不同 o 您正在读取不同的“TEACHERS”表
在链接服务器（而不是本地）上实际运行两个链接 SQL 语句会给您带来什么？
Just thoughts...
Same server? That is, linked server is different in target or credentialss o you are reading a different "TEACHERS" table
What does running both linked SQL statement actually on the linked server (not locally) give you?
由于 NVL()，第二个查询永远不会为教师表返回 null，因此它可以根据数据返回更多记录。
基本上“and schoolloginid is not null”永远不会被击中，因为你用“”替换了空值
Second query never would return a null for the teachers table because of the NVL() so it could return more records depending on the data.
basically the " and teacherloginid is not null " never gets hit because you replace the nulls with ""