获取记录不在本地数据库中但在远程数据库中

Question

寻找正确的语法，了解如何获取在主数据库中执行“NOT EXISTS”但在远程数据库中执行的所有记录

以下代码从远程数据库获取所有空白记录，不确定它是否与本地数据库有关。

<asp:AccessDataSource ID="AccessDataSource1" runat="server" DataFile="<%$ ConnectionStrings:accessConnectionString %>"      
    SelectCommand="SELECT EnrollmentsTbl.UserName, EnrollmentsTbl.SubmitTime, EnrollmentsTbl.ClassName, 
    EnrollmentsTbl.ClassDate, EnrollmentsTbl.ClassTime, EnrollmentsTbl.Enrolled, EnrollmentsTbl.WaitListed, EnrollmentsTbl.Instructor, 
    EnrollmentsTbl.DateCompleted, EnrollmentsTbl.Completed, EnrollmentsTbl.Walkin 
    FROM [;DATABASE=e:\subsite.mdb].EnrollmentsTbl AS XXX 
    LEFT JOIN EnrollmentsTbl ON XXX.UserName = EnrollmentsTbl.UserName WHERE (EnrollmentsTbl.UserName Is Null)">
</asp:AccessDataSource>

Answer 1

＆＃34;标准＆＃34;方法是使用外连接并对空值进行过滤，将其解释为：

select r.*
from remote_table r
left join local_table l
  on l.id = r.id
where l.id is null

Answer 2

这是最终的解决方案：

<asp:AccessDataSource ID="AccessDataSource1" runat="server" DataFile="<%$ ConnectionStrings:accessConnectionString %>"      
    SelectCommand="SELECT XXX.UserName, XXX.SubmitTime, XXX.ClassName, 
    XXX.ClassDate, XXX.ClassTime, XXX.Enrolled, XXX.WaitListed, XXX.Instructor, 
    XXX.DateCompleted, XXX.Completed, XXX.Walkin 
    FROM [;DATABASE=e:\subsite.mdb].EnrollmentsTbl AS XXX 
    LEFT JOIN Users ON XXX.UserName = Users.UserName WHERE (Users.UserName Is Null)">
</asp:AccessDataSource>