Mongo - 查询，嵌入式文档不匹配，除了点符号

问题描述

i am confuse.here is the example:

MongoDB Enterprise > db.employee.find()

result:

{"_id":1002,"name":"Jack","address":{"previous":"Cresent Street","current":"234,Bald Hill Street","unit":"MongoDB" } }

I try this:

db.employee.find({address:{previous: "Cresent Street"}})

result: nothing returns

Next a try this:

 db.employee.find({"address.previous": "Cresent Street"})

result:

{"_id":1002,"name":"Jack","address":{"previous":"Cresent Street","current":"234,Bald Hill Street","unit":"MongoDB"}}

The question is wath is wrong with this?

i useMongoDB shell version v4.2.7 installedcmd db.version() 4.2.6debian 10.4

thanks for your replies.

解决方案

When you Query on Embedded/Nested Documents using dotted field notation

{"address.previous": "Cresent Street"}

means find a document that containd an address field that contains a document whose previous field is equal to "Cresent Street".

When you provide a subdocument like

{address:{previous: "Cresent Street"}}

this means to find a document that contains an address field whose content is exactly the document {previous: "Cresent Street"}, with no additional fields. If you provide multiple fields in the subdocument, field order also matters.

Both of these queries are useful in specific scenarios, pick the one that does what you need in your situaion.

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