ADO.NET ExecuteScalar()用法

string sqlInsert = "insert into YJ_YEWU(BGBH,BGFS,JYLX,CPMC,GGXH,YPPH,ZCSB,CPDJ,YPSL,SCRQ,CYJS,CPZL,RWLY,HZBS,SJDW_DWMC,SJDW_LXDZ,";
        sqlInsert += "SJDW_LXR,SJDW_LXDH,SJDW_YZBM,SCDW_DWMC,SCDW_LXDZ,SCDW_LXR,SCDW_LXDH,SCDW_YZBM,WTDW_DWMC,WTDW_LXDZ,WTDW_LXR,WTDW_LXDH,";
        sqlInsert += "WTDW_YZBM,JYBZ,WTTSYQ,SYR,SYRDH,SYRQ,CYR,CYRQ,CYDD,JCFYRY,CYDH,FYZT,YPCLFS,UserName,JYXM,JYSM,JYJL,JYJLTRUE,SJDW_ID,";
        sqlInsert += " SCDW_ID,WTDW_ID,BYSL,BYDD,BaseName)";
        sqlInsert += "(select BGBH,BGFS,JYLX,CPMC,GGXH,YPPH,ZCSB,CPDJ,YPSL,SCRQ,CYJS,CPZL,RWLY,HZBS,SJDW_DWMC,SJDW_LXDZ,";
        sqlInsert += "SJDW_LXR,SJDW_LXDH,SJDW_YZBM,SCDW_DWMC,SCDW_LXDZ,SCDW_LXR,SCDW_LXDH,SCDW_YZBM,WTDW_DWMC,WTDW_LXDZ,WTDW_LXR,WTDW_LXDH,";
        sqlInsert += "WTDW_YZBM,JYBZ,WTTSYQ,SYR,SYRDH,SYRQ,CYR,CYRQ,CYDD,JCFYRY,CYDH,FYZT,YPCLFS,UserName,JYXM,JYSM,JYJL,JYJLTRUE,SJDW_ID,";
        sqlInsert += " SCDW_ID,WTDW_ID,BYSL,BYDD,BaseName from Temp_YEWU where YEWUID='" + TempYEWUID + "')select @@identity";
       
        myConn.Open();
        myCmd = new SqlCommand(sqlInsert, myConn);
        newYEWUID = Int64.Parse(myCmd.ExecuteScalar().ToString());  //取得新插入记录的ID值
        myConn.Close();

        string sqlUpdate = "update Temp_YEWUXM set YEWUID=" + newYEWUID + " where YEWUID=" + TempYEWUID;
       
        myConn.Open();
        myCmd = new SqlCommand(sqlUpdate,myConn);
        myCmd.ExecuteNonQuery();
        myConn.Close();