"MongoDB Learning Note 14" MongoDB Query: Find basics

MongoDB uses find to query, returning a subset of the documents in a collection;

Returns all documents in the Document collection blog:

> Db.post.find () {"_id": ObjectId ("54a530c3ff0df3732bac1681"), "id": 2, "name": "Joe", "age": +, "sex": 1, "SC Hool ":" Marry "} {" _id ": ObjectId (" 54a530c3ff0df3732bac1680 ")," id ": 1," name ":" Joe "," age ": +," comments ": [ "Test2", "Test9", "Test5"], "sex": 1, "school": "Marry"} >

Returns the specified document:

> Db.post.find ({"id": 1}) {"_id": ObjectId ("54a530c3ff0df3732bac1680"), "id": 1, "name": "Joe", "Age": "comme NTS ": [" Test2 "," Test9 "," Test5 "]," sex ": 1," school ":" Marry "} >

Returns the specified key value:

> db.post.find ({},{"id": 1, "Age": 1}) {' _id ': ObjectId ("54a530c3ff0df3732bac1681"), "id": 2, "age": $ {"_id" : ObjectId ("54a530c3ff0df3732bac1680"), "id": 1, "Age": >

The default is always to return the "_id" key, and the following method can not return "_id" key:

> db.post.find ({},{"id": 1, "Age": 1, "_id": 0}) {"id": 2, "age": +} {"id": 1, "Age": +} >

You can combine multiple criteria, such as querying a document with the name "Joe" and an ID of 1:

> db.post.find ({"Name": "Joe"})    {  "_id"  : objectid (" 54a530c3ff0df3732bac1681 "), " id " : 2, " name " : " Joe ", " Age " : 30,   "Sex"  : 1,  "school"  :  "Marry"  }    {  "_id"  :  objectid ("54a530c3ff0df3732bac1680"),  "id"  : 1,  "name"  :  "Joe",  "age"  : 30,  "Comments"  : [  "Test2",  "Test9",  "test5"  ],  "Sex"  : 1,  "School"  :  "Marry"  }    > db.post.find ({"Name" : "Joe", "id": 1})     {  "_id"  : objectid ("54a530c3ff0df3732bac1680"),  "id " : 1, " name " : " Joe ", " age " : 30, " comments " : [  "Test2",  "Test9",  "test5"  ],  "Sex"  : 1,  "school"  :  "Marry"  }     >

This article is from the "Margin with Wish" blog, please be sure to keep this source http://281816327.blog.51cto.com/907015/1599149

"MongoDB Learning Note 14" MongoDB Query: Find basics