等级为空的时候。查询哪三个字段的平均值？

select 

roast_season,

smoke_area,

smoke_type,

${if(len(smoke_level)=0,"AVG(standard_slice_rate) as 出片率,AVG(standard_stem_rate) as 含梗率,

AVG(avg_slice_water) AS 含水率 ","smoke_level,AVG(standard_slice_rate) as 出片率,

AVG(standard_stem_rate) as 含梗率,

AVG(avg_slice_water) AS 含水率")}

from physics_check 

group by roast_season,smoke_area,

${if(len(smoke_level)=0,"","smoke_level,")}

smoke_type order by roast_season

直接  like  '%参数%' 就可以的吧

select 

roast_season,smoke_area,smoke_level,smoke_type,

AVG(standard_slice_rate) as 出片率,

AVG(standard_stem_rate) as 含梗率,

AVG(avg_slice_water) AS 含水率 

from physics_check 

where 1=1

${if(len(等级)=0,""," and smoke_level in ('"+等级+"')")}

group by roast_season,smoke_area,smoke_level,smoke_type 

order by roast_season