参考文章-https://www.cnblogs.com/melonjiang/p/6536876.html
_id
相同会报错_id
相同会更新其余的字段db.collection.update({},{$set:{name:"a"}},{multi:true})
$in
db.collection.find({name:{$in:["a","b","c"]}})
$nin
db.collection.find({name:{$nin:["a","b","c"]}})
db.collection.find({name:"a",age:20})
bd.collection.find({$or:[{name:"a"},{age:20}]})
db.collection.find({}).sort({age:1})
db.collection.distinct(“gender”,{age:{$gt:18}})
分组 db.collection.aggregate({group:{_id:"
project db.collection.aggregate( {group:{_id:"sum:1}}}, {project:{_id:0,age:"
match db.collection.aggregate( {match:{gender:true}, {group:{_id:"age",count:{project:{_id:0,age:"
db.tv1.aggregate(
{$project:{title:1,_id:0,count:"$rating.count",rate:"$rating.value",country:"$tv_category"}},
{$match:{rate:{$gt:8}}},
{$group:{_id:"$country",count:{$sum:1}}},
{$project:{_id:0,country:"$_id",count:1}}
)
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