SSMA转换

Question

我在Access中有以下查询，但在使用SSMA时它不会转换为SQL。转换器提供以下与IIf语句相关的错误

*   SSMA error messages:
   *   A2SS0061: The identifier 'IIf(BOOLEAN, VARCHAR, UNKNOWN)' was not converted.
   *   A2SS0061: The identifier 'IIf(BOOLEAN, VARCHAR, UNKNOWN)' was not converted.
   *   A2SS0061: The identifier 'IIf(BOOLEAN, VARCHAR, UNKNOWN)' was not converted.
   *   A2SS0061: The identifier 'IIf(BOOLEAN, VARCHAR, VARCHAR)' was not converted.

任何想法都会受到最高的赞赏。

    SELECT tblkpitracking.kpitrackingday,
       tblkpitracking.kpitrackingweek,
       tblkpitracking.kpitrackingmonth,
       tblkpitracking.kpitrackingvalue,
       tblworkstream.workstreamshorthand,
       tblworkstream.workstream,
       tblworkstreamkpi.kpiid,
       tblkpitracking.workstreamkpiid,
       Iif([unit] = '--', '', [unit]) &
       Iif([bytimeperiod] = '--', '', [bytimeperiod])
       & Iif([byunit] = '--', '', [byunit]) &
       Iif([unit] = '--'
           AND [bytimeperiod] = '--'
           AND [byunit] = '--', 'TBD', '') AS
       CleanKPI,
       [workstreamshorthand] & ': ' & [cleankpi]
       AS WorkStreamShortKPIClean,
       [workstream] & ': ' & [cleankpi]
       AS WorkStreamKPIClean,
       tblworkstreamkpi.kpiclarification,
       tblworkstreamkpi.kpibaselinevalue,
       tblworkstreamkpi.kpitargetvalue
FROM   tblworkstream
       INNER JOIN ((tblunits
                    INNER JOIN ((tblbyunits
                                 INNER JOIN (tblbytimeperiod
                                             INNER JOIN tblkpi
                                                     ON
                                             tblbytimeperiod.bytimeperiodid
                                             =
                                             tblkpi.bytimeperiodid)
                                         ON tblbyunits.byunitsid =
                                            tblkpi.byunitsid)
                                INNER JOIN tblworkstreamkpi
                                        ON tblkpi.kpiid =
                               tblworkstreamkpi.kpiid)
                            ON tblunits.unitsid = tblkpi.unitsid)
                   INNER JOIN tblkpitracking
                           ON tblworkstreamkpi.workstreamkpiid =
                              tblkpitracking.workstreamkpiid)
               ON tblworkstream.workstreamid = tblworkstreamkpi.workstreamid;