string sql4 = string.Empty;
                    sql4 = @"select device.id from device, event1 where device.IDENTIFY=event1.MC_HOST_ADDRESS and device.TYPE=event1.MC_ORIGIN_CLASS and device.OBJECT =event1.MC_OBJECT_OWNER  and device.TYPE='服务器'
                            union all
                            select device.id from device, event1 where device.IDENTIFY=event1.MC_HOST_ADDRESS and device.TYPE=event1.MC_ORIGIN_CLASS and device.OBJECT =event1.MC_OBJECT_OWNER and device.SUBOBJECT=event1.MC_OBJECT and device.TYPE='数据库'
                            union all
                            select device.id from device, event1 where device.IDENTIFY=event1.MC_HOST_ADDRESS and device.TYPE=event1.MC_ORIGIN_CLASS and device.OBJECT =event1.MC_OBJECT_OWNER and device.SUBOBJECT=event1.MC_OBJECT and device.TYPE='中间件' ";
                           
                        oc.ExecuteReader(sql4);
                   //     int "+id+" = oc.ExecuteReader(sql4);

                        if( "+id+" != null)


                        {   string sql5 = string.Empty;
                     sql5=@"insert into alert (alert.id,alert.eventid,alert.deviceid,alert.status,alert.parameter,alert.value,alert.severity,alert.msg,alert.ticketid,alert.ticketstatus,alert.timestamp,alert.createtime,alert.lastmodifiedtime) values ('9999',event1.mc_tool_sev,
 '+id+',event1.status,event1.MC_PARAMETER,event1.mc_parameter_value,'2',event1.msg,event1.mc_object_uri,event1.mc_service,event1.MC_INCIDENT_TIME,event1.MC_ARRIVAL_TIME,event1.DATE_RECEPTION)";
                     oc.ExecuteReader(sql5);
                        
                        }

                        
                        else;


                        {
                         return;
      
                        }

我在sql里查出来的id  可以直接if( "+id+" != null) 使用吗

C#，你发错版了，这里是C++版。
if( "+id+" != null) 你这是什么意思？一个常量字符串和null值进行不等比较？表达式结果永远为真。

你帮我看下被 谢谢了
那我改成
  oc.ExecuteReader(sql4);
                    int id = oc.ExecuteReader(sql4);

                        if( id!= null)
｛。。。
｝
可以吗

不会 顺便学习一下