Question

查询出了什么问题？

select * 
from ERP.dbo.Table 
where storeID in (case 
                     when @Designation = 80 
                        then 
                           (select storeID 
                            from ERP.dbo.Store 
                            where companyID = @CompanyID 
                              and isMonitoringAvailable = 1  
                              and storeID = ISNULL(@StoreId, storeID)) 
                        else 
                           (select storeID 
                            from ERP.dbo.EmployeeRole 
                            where employeeID = @EmployeeId 
                              and storeID = ISNULL(@StoreId,storeID) )  
                 end)

我收到此错误：

Msg 512，第16级，状态1，第46行
子查询返回的值超过1。子查询时不允许这样做遵循=，！=，<，<=，>，> =或将子查询用作表达式时。

Answer 1

您可以通过以下方式重新编写条件

select * from ERP.dbo.EmployeeRole where
  ( storeID in (          
  (select storeID 
     from ERP.dbo.Store 
    where companyID=@CompanyID and isMonitoringAvailable=1  
      and storeID=ISNULL(@StoreId,storeID)
        ) and @Designation=80
    ) Or
   storeID  in (Select storeID 
           from ERP.dbo.EmployeeRole 
          where employeeID=@EmployeeId 
            and storeID=ISNULL(@StoreId,storeID)
               )

您的查询返回错误，因为然后，否则结果生成多个storeid

Answer 2

UNION ALL期望expressions，因此出现错误。从性能角度考虑，替代方法是使用select * from ERP.dbo.EmployeeRole where @Designation=80 AND storeID in ( select storeID from ERP.dbo.Store where companyID=@CompanyID and isMonitoringAvailable=1 and storeID=ISNULL(@StoreId,storeID) ) UNION ALL select * from ERP.dbo.EmployeeRole where @Designation<>80 AND storeID in ( select storeID from ERP.dbo.EmployeeRole where employeeID=@EmployeeId and storeID=ISNULL(@StoreId,storeID) )运算符，如下所示：

IF-ELSE

另一种方法是使用UNION ALL，但是if (context.Users.Where(u => u.Username.Equals((string) value, StringComparison.OrdinalIgnoreCase)).Count() >= 1) { return new ValidationResult("Username is already taken", new [] { "Username" }); }会更好。

在子句中的SQL情况

2 个答案: