查询全部文档
db.getCollection('user').find({})
------------------------------------------------------------------------------------------------------------------------------
条件查询:db.集合.find({"查询条件"},{"指明需要查询出来的字段【1:显示,0:不显示】"})
mongo查询:db.user.find({"age": {$gte: 21}}, {"age": 1,"name": 1})
sql查询:select age,name from user
mongo查询:db.user.find({"age": {$lte: 22}, $or:[{"hobby.name": "跳舞"},{"hobby.type": "户外"}]})
sql查询:where age >= 22 and (hobby.name='跳舞' or hobby.type='户外')
------------------------------------------------------------------------------------------------------------------------------
查询文档总数:
db.oders.count()
------------------------------------------------------------------------------------------------------------------------------
删除操作
db.score.deleteOne({"删除条件"})
db.score.deleteMany({"删除条件"},{"删除条件"}) {}之内是and的关系,{}之外是or 的关系