MongoDB Query-Notes

# MONGODB Query Statement

MongoDB: Distributed File Store database, between relational database and non-relational database, Concept: collection (table), document (row), Field (column)

tychtml Database:
# 1. Number of document queries

? Db.getcollection (' companys '). Find ({}). Count ()

# # 2, find ()

Db.getcollection (' companys '). Find ({"_id": ObjectId ("59c12543e1382308c4e0f786")})

? = select * from companys where _id= "59c12542e1382308c4e0f262"

Db.getcollection (' companys '). Find ({},{"summary": 1})

? =select Summary from Companys

Inline document query:
Db.getcollection (' companys '). Find ({"Summary.reportcount": 4}). Limit (1)
Db.getcollection (' companys '). Find ({"Staffcount": {$elemMatch: {"position": "Supervisor", "name": "Song Jialin"}}}). Limit (1)
Db.getcollection (' companys '). Find ({"Summary.reportcount": 4, "Summary.checkcount": 1}). Limit (1)
MongoDB provides a set of comparison operators:

|  $lt | < |
| :--: | :--: |
|  $lte | <= |
|  $GT | > |
|  $gte | >= |
|  $ne | !=  |

Delete database: Db.dropdatabase ()

View all databases: Show DBS

Create DATABASE: Use Runoob

Insert Document: DB. Collection_name (document)

Update document: Db.collection.update ()

Querying using the $elemmatch operator

Fuzzy Query $regex

MongoDB Update has two commands: Update\save
Data Update operators:
$inc:
Usage: {$inc: {Field:value}}
Function: Adds value to a field of a number
Example: {"_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "name": "Chenzhou", "Age": 22}
Increase the age of 5 for students with name Chenzhou
Db.students.update ({"Name": "Chenzhou"},{$inc: {"Age": 5}})
$set:
Usage: {$set: {Field:value}}
Function: Sets the value of a field in a document
$unset:
Usage: {$unset: {field:1}}
Role: Delete a field
Cases:
Db.students.update ({"Name": "Chenzhou"},{$unset: {"Age": 1}})
$push:
Usage: {$push: {Field:value}}
Function: Append value To field, (field can only be an array type, if field does not exist, an array type is automatically inserted)
$PUSHALL:
Usage: {$pushAll: {Field:value_array}}
Function: Use same as $push, just $pushall can append multiple values to an array field at a time
$addToSet:
Usage: {$addToSet: {Field:value}}
Function: Adds a value to the array, and only increases if the value does not exist in the array.
$pop:
Usage: Delete the first value in the array: {$pop: {field:-1}}, delete the last value in the array: {$pop: {field:1}}
Function: Used to delete a value within an array
$pull:
Usage: {$pull: {Field:_value}}
Function: Removes a value equal to _value from the array field
$PULLALL:
Usage: {$pullAll: Value_array}
Function: Use same as $pull, you can delete multiple values in an array at once
$rename:
Usage: {$rename: {old_field_name:new_field_name}}
Role: Renaming a field

MongoDB Query-Notes