MongoDB (5) Document CRUD operations

MongoDB Getting Started column

Http://blog.csdn.net/column/details/19681.html

MongoDB document CRUD Operations
Querying documents The basic syntax for querying a document using MongoDB is as follows:

Db.collection_name.find (query, projection) # Return data in compressed format

Db.collection_name.find (query, projection). Pretty () # return data in easy-to-read format

Query: Optional, use the query operator to specify the criteria;
Projection: optional, use the projection operator to specify the returned key, and if you need to return all keys in the document, simply omit the parameter;

# Querying all documents in the Testdb.artciles collection

> Use TestDB

> Db.articles.find (). Pretty ()

# Querying documents author= ' Assad ' in the Testdb.articles collection

> Db.atricles.find ({author: ' Assad '})

Query condition operator

Operator	Meaning and syntax	Example
Compare Query characters
:	equals (=); {<key>:<value>}	Db.col.find ({name: ' Assad '}) Querying documents for name= ' Assad '
$ne	Not equal to (! =); {<key>:{$ne: <value>}}	Db.col.find ({name:{$ne: ' Assad '}}) Querying documents for name!= ' Assad '
$lt	Less Than (<): {<key>:{$lt: <value>}}	Db.col.find ({score:{$lt: 120}}) Querying documents for SCORE>120
$gt	Greater than (>); {<key>:{$gt: <value>}}	Db.col.find ({score:{$gt: 120}}) Querying documents for SCORE<120
$lte	Less than or equal to (<=); {<key:{$lte: <value>}}	Db.col.find ({score:{$lte: 120}}) Querying documents for SCORE<=120
$gte	Greater than or equal to (>=); {<key>:{$gte: <value>}}	Db.col.find ({score:{$gte: 120}}) Querying documents for score>= 120
Logical relation Query character
$and	and and relationships; {$and: [Query1, Query2]} {Query1, Query2}	Db.col.find ({$and: [{city: ' Guangzhou '}, {score:{$gt: 250}}]}) Db.col.find ({city: ' Guangzhou ', score:{$gt: 250}} Query city= ' guangzhou ' and core>250 documents
$or	or or relationship; {$or: [Query1, Query2]}	Db.col.find ({$or: [{city: ' Guangzhou '}, {score:{$gt: 250}}]}) Querying documents city= ' Guangzhou ' or core>250
$nor	nor XOR or relationship; {$nor: [Query1, Query2]}	Db.col.find ({$nor: [{city: ' Guangzhou '}, {score:{$gt: 250}}]}) Documents for querying (city= ' Guangzhou ' or core<=250) and (city!= ' Guangzhou ' and core > 250)
$not	Non-relationship; {$not: {query}}	Db.col.find ({$not: {city: ' Guangzhou '}}) Querying documents for city!= ' Guanhgzhou '
Member Relations Query character
$all	The query key matches the result of all the members in the specified array; {<key>:{$all: [Array]}}	Db.col.find ({tages:{$all: [' Java ', ' CPP ', ' Linux '}}) Query tages field array containing ' Java ', ' CPP ', ' Linux ' all these values of the document
$in	The query key matches the result of any of the members in the specified array; {<key>:{$in: [Array]}}	Db.col.find ({tages:{$in: [' Java ', ' CPP ', ' Linux '}}) Query a tages field array containing ' Java ', ' CPP ', and ' Linux ' for any of the values in the document
$nin	The query key does not match the result of any of the members in the specified array; {<key>:{$in: [Array]}}	Db.col.find ({tages:{$in: [' Java ', ' CPP ', ' Linux '}}) Query Tages field array does not contain ' Java ', ' CPP ', ' Linux ' documents
.	Query key to specify subscript member, index starting from 0; {<key.index>:query}	Db.col.find ({tages.1: ' java '}) Query tages field Array 2nd element = ' Java ' document
Value Property Query character
$size	Querying arrays of specified lengths {<key>:{$size: value}}	Db.col.find ({tages:{$size: 3}}) Querying a document with a length of 3 tages field array can be combined with a comparison query
$type	To query the specified type of key, see the list of specific types: Https://docs.mongodb.com/manual/reference/operator/query/type/index.html {<key>: {$type: TypeCode}}	Db.col.find ({title:{$type: 2}}) Querying a document with the title type String
$exits	Querying a document that specifies the key for which the condition exists {<key>:{$exists: <boolean>}}	Db.col.find ({school:{$exits: false}}) Querying all documents that do not exist in the school field
Null	is not actually an operator, it is a placeholder for null values {<key>:null} {<key>:{$in: [NULL]}}	Db.col.find ({school:null}) The Query school field does not exist, or the school field value is empty document Db.col.find ({school:{$in: [null], $exists: true}}) Query school field exists, but the value is empty document
$regex	Regular matching of strings, using Perl-compatible expressions, can be used to achieve similar SQL like clause effect; {<key>:{$regex:p attern, $options: Ops}} Where $options is used to decorate the regex with the following parameters: -I: Ignore case; -X: Force a branch to a string without a callout \ n; -The dot in s:pattern matches all characters (including line break); -X: Ignores special characters that are not escaped in pattern;	Db.col.find ({name:{$regix: "^a*"}}) Db.col.find ({name:/^a*/}}) Querying a document whose name begins with a Db.col.find ({name:{$regex: "^a*", $options: ' I '}}) Db.col.find ({name:/^a*/i}) Query the name of a document that starts with a, or is slightly case-sensitive
$where	Use any JavaScript as part of the query, including JS expressions and JS closures; {$where: Javascript-operation} In the JS expression, use This,obj to refer to each Document object	Db.col.find ({$where: "This.score > This.salary"}) Db.col.find ({$where: "Obj.score = this.salary"}) Db.col.find ({$where: function () {return (This.score > This.salary)}}) Querying all score > Salary documents in col;

> Use TestDB

# Querying documents author= "Assad" in the Testdb.articles collection

> Db.articles.find ({author: ' Assad '})

# Find documents for likes > 1000

> Db.articles.find ({likes:{$gt: 1000}})

# Query for documents with likes greater than 1000, less than 1500

> Db.artciles.find ({likes:{$gt: $, $LT: 1500}})

# query Author= "Assad" simultaneously likes > 2000 documentation

> Db.articles.find ({author: ' Assad ', likes:{$gt: 2000}})

# Querying documents authoer= "Assad" or "vancy"

> Db.articles.find ({author:{$in: [' Assad ', ' vancy ']}})

# query Tages array containing ' Java ', ' Groovy ' documents