Learn MongoDB Four: MongoDB query (i)

Original: http://blog.csdn.net/congcong68/article/details/46841075

First, Introduction

MongoDB provides a db.collection.find () method that can be implemented based on conditional queries and specifies that fields returned using the projection operator omit this parameter to return all fields in the matching document.

Two Db.collection.find () Querying data

Grammar

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1. > Db.collection.find (query,projection)

Parameters	Type	Describe
Query	Document	Optional. Using query operators to specify query criteria
Projection	Document	Specifies that fields returned using the projection operator omit this parameter to return all fields in the matching document

Projection syntax:

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1. {field1: <boolean>, Field2: <boolean> ...}

Description

1 or True indicates the return field

0 or False indicates that the field is not returned

_ID: The default is 1, not specifying that the field will be returned by default, unless it is set to 0, the field will not be returned.

Specify the return field, sometimes the document field is many and the data is large, we specify to return the fields we need, so as to save the amount of data transferred, reduce memory consumption, improve performance, when the data is large, performance is obvious.

1. Querying data

(1) Returns all documents in the collection:

Db.collection.find ()

Or

Db.collection.find ({})

Like the SQL statement:

SELECT * from TABLENAME

(2) Specifies that fields returned using the projection operator omit this parameter to return all fields in the matching document

Grammar:

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1. Db.orders.find ({},{field1: <boolean>, Field2: <boolean> ...})

Example:

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1. >db.orders.find ({},{"Onumber": 1,"CNAME": 1})

And the _id default setting is 1, and all returns back

You can set _id not to return

Example:

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1. >db.orders.find ({},{"Onumber": 1,"CNAME": 1,"_id": 0})

2. Search by condition (1) equals conditional query

Grammar:

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1. >db.collect.find ({<field1>: <value1>,<field2>: <value2>, .....})

Example:

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1. >db.orders.find ({"onumber":"002"})

Find documents for ONUMBER=002

(2) comparison operators

$GT (greater than), $GTE (greater than or equal to), $lt (less than), $lte (less than or equal to)

Grammar:

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1. {<field1>: {<expression1>},<field2>: {<expression1>}, ...}

1) $gt (greater than) comparison operator

Example:

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1. >db.orders.find ({"Onumber": {$gt:"003"}})

We're looking for onumber>003 with a value of only 004.

2) $gte (greater than or equal to) union query with $lte (less than or equal to) and specify return field (via second parameter)

Example:

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1. >db. Orders. Find ({"Onumber": {$gte: "002", $lte: "003"}},{"Onumber": 1, "CNAME": 1})

We look for 002=<onumber<=003 and specify the return Onumber and CNAME fields, and the _id default setting is 1, and all returns back

(3) Search for $or, and $and conditions

1) Query $and conditions

Grammar:

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1. {$ and: [{<expression1>}, {<expression2>}, ...,]}

The syntax for simple usage:

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1. {<field1>: <value1>,<field2>: <value2>,. ...}

Example:

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1. >db.orders.find ({"onumber":"002","CNAME":"Zcy2"})

Finding onumber=002 and Cname= zcy2 querying documents

2) $or (or) conditional query

Grammar:

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1. {$nor: [{<expression1>}, {<expression2>}, ...]}

Example:

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1. >db.orders.find ({$or:[{"onumber":"002"},{"CNAME":"Zcy1"}]})

Our conditions onumber=002 or cname= zcy1 find documents that meet onumber=002 or cname= zcy1 conditions

3) $or and $and joint condition query

Example:

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1. >db.orders.find ({$and:[{"date":"2015-07-01"},{$or:[{"onumber":"002"},{"CNAME":  "Zcy1"}]}]})

The document of the query condition Date=2015-07-01and (onumber=002 or cname=zcy1) is either equal to the date equals 2015-07-01 and to satisfy Onumber equals 002 or CNAME equals zcy1 one of them.

(4) $in (inclusive), $nin (not included) condition inquiry

1) $in (included) criteria query

Grammar:

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1. {field: {$ in: [<value1>, < Value2>, ...]}}

Example:

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1. >db.orders.find ({"Onumber": {$in:["001","002"]}})

The document that queries Onumber in ("001", "002") conditions is Onumber equals 001 or equals 002 This is a bit like $or, but when $or is a conditional query, you can specify a different field: Db.orders.find ({$or: [{" Onumber ":" 002 "},{" CNAME ":" Zcy1 "}]})

, and $in only for one field.

2) $nin (not included) criteria query

Grammar:

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1. {field: {$nin: [<value1>, < Value2>, ...]}}

$nin (not included) the opposite of $in (inclusive), there is no specific introduction

(5) $not (not equal to) condition query

Grammar:

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1. {field: {$ not: {< expression1>}}}

$not operator cannot be used independently and must be used with other operating conditions (except $regex)

Example:

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1. >db.orders.find ({"Onumber": {$not:{$gt:"002" }}})

Find Onumber is not equal to more than 002 of document data

(6) $exists used to determine whether a field exists

Grammar:

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1. {field: {$ exists: < boolean>}}

Example:

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1. >db.orders.find ({"age": {$exists:true}})

Without the element of age, nothing comes back.

Insert an age element and perform a

(7) $mod modulo and equals the specified value

Grammar:

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1. {field: {$mod: [Value, value2]}}

For the element field value, modulo the value of value to value2 the document data

Example:

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1. >db.orders.find ({"age": {$mod: [5,1]}})

For the value of the age element and 5 modulo, the value of the modulo is equal to 1 of the document data

(8) Null lookup element does not exist and the element corresponds to a document with a value of NULL

Grammar:

{Field:null}

Example:

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1. >db.orders.find ({"age":null})

1) Find the age element exists and the value equals null

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1. >db.orders.find ({"age": {$in:[null], $exists:True}})

(9) $type to match the type of an element

Grammar:

{field: {$type: <;}}

Number is the type value corresponding to the type used in MongoDB

Type		Type value
Double	1
String	2
Object	3
Array	4
Binary data	5
Undefined (deprecated)	6
Object ID	7
Boolean	8
Date	9
Null	10
Regular Expression	11
Javascript	13
Symbol	14
JavaScript (with scope)	15
32-bit integer	16
Timestamp	17
64-bit integer	18
Min Key	255
Max Key	127

Learn MongoDB Four: MongoDB query (i)