今天有一个业务涉及到mongodb的多表查询，大体记录下语句结构
db.table_a.aggregate([
{$lookup:{from:"table_b",localField:"userid",foreignField:"userid",as:"organization_doc"}}, //联表B
{
$project:{
_id:1,
cardid:1,
checkin_time:1,
checkin_date:1,
userid:1,
selfcare_ability:1,
checkout_time:1,
checkout_date:1,
inventory_doc:"$organization_doc.name"
} //通过project参数限制返回数据，提高效率
},
{$lookup:{from:"table_c",localField:"cardid",foreignField:"cardid",as:"archives_doc"}}, //联表c
{$match:{"archives_doc.xingzheng_code" : "370213000001"}}, //匹配搜索条件condition
{$limit:10},{$skip:1}]) //其他参数，如条数显示，翻页，排序等