主体SQL：

SELECT *  FROM campus_area where 1=1

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

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

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

department SQL：
select department from campus_area

campus_name SQL:

SELECT distinct campus_name  FROM campus_area

where department in ('${department}')  and area in ('${area}')

area SQL:

SELECT distinct area FROM campus_area

where department in ('${department}')