ssrs order by case isnull-查询工作,ssrs错误

查询可以正常工作并按应该的方式排序。但是当SSRS数据集的一部分出现查询错误。 错误按大小写表达式的顺序缩小,如图所示。语法被接受。 运行期间的第一条错误消息:“报告处理期间发生错误。(rsprocessingaborted)“ 错误弹出窗口的详细信息按钮显示下面的Try n错误。

select  <columns>
from    <view>
where   <criteria>
order by 

> error condition - try 1
        -- errors "The isnull function requires 2 argument(s)."
        case when isnull(<parm>, '') <> '' 
             then <column to be sorted>
        end, 

> error condition - try 2
        -- errors "An expression of non-boolean type specified in a context where a condition is expected, near ..."
        case when (<parm> is not null  or 
                   <parm> <> '')
             then <column to be sorted>
        end, 

> error condition - try 3
        -- errors "An expression of non-boolean type specified in a context where a condition is expected, near ..."
        case when <parm> is not null 
             then <column to be sorted>
             when <parm> <> ''
             then <column to be sorted>
        end, 

        <more columns to sort>