支持啊 你帮助文档搜参数为空 选择全部 里面的就是这样的写法

where ${if(len(自定义参数名) == 0,"","and  字段名称 ='" + 自定义参数名+ "'")} 

太能了，参考下吧，下面配套的是SqlServer2018  

WHERE 1=1 AND DeleteFlag = 0 

  AND  USER_CODE = $fine_username

  ${if(len(USER_CODE) = 0,""," and [YearMonth]  = '" + yearmonth + "'")}

${if(len(yearmonth) = 0,""," and [YearMonth]  = '" + yearmonth + "'")}

${if(len(attributiontype) == 0 || attributiontype=0," ","and attributiontype in (SELECT VALUE FROM STRING_SPLIT('"+ attributiontype +"',','))")}

${if(len(regiontreeid) = 0,""," and [MasterDeptTreeId] = '" + regiontreeid + "'")} 

${if(len(region) = 0,""," and [MasterDeptName] = '" + region + "'")}

SELECT * FROM 订单 
WHERE 1=1  
${if(len(area) == 0,"","and 货主地区 = '" + area + "'")}

这样就可以咯DEMO:https://help.finereport.com/uploads/file/20190904/1567597557319444.cpt
http://下拉框参数为空选择全部-https://help.finereport.com/doc-view-2394.html