MongoDB Data Update command

One, mongodb Data Update command

MongoDB Update has two commands: Update, save.

1.1update command

UPDATE command format:

Db.collection.update (Criteria,objnew,upsert,multi)

Parameter description:

Criteria: Query criteria

Objnew:update objects and some update operators

Upsert: If there is no record of update, whether to insert objnew this new document, true to insert, default to False, not to insert.

Multi: The default is false, updating only the first record found. If true, all records that are queried by criteria are updated.

Example:

Shell Code

2. > Db.classes.insert ({"name":"C1","Count": $)
4. > Db.classes.insert ({"name":"C2","Count": $)
6. > Db.classes.find ()
8. { "_id": ObjectId ("5030f3a3721e16c4ab180cd9"), "name": "C1", "Count": $
10. { "_id": ObjectId ("5030F3AB721E16C4AB180CDA"), "name": "C2", "Count": /c13>
12. >

Example 1: Change the class name of count greater than 20 to C3

Shell Code

1. > db.classes.update ({20}},{$set: {
2. > db.classes.find ()   
3. {  "5030F3A3721E16C4AB180CD9"),  30 }   
4. {  "_id"  :  ObjectId ( "5030F3AB721E16C4AB180CDA"),   "C2",  30 }  
5. >   

Because the values of Upsert and multi are not specified, all defaults to false, as the result shows, only the first record that meets the criteria is modified.

Example 2: Change the class name of count greater than 20 to C4, set multi to True

Shell Code

1. > db.classes.update ({20}},{$set: {
2. > db.classes.find ()   
3. { " 5030F3A3721E16C4AB180CD9 "),  " name "  :  "C4",  30  }  
4. {  "_id"  :  objectid ( "5030F3AB721E16C4AB180CDA"),   "C4",  30 }   
5. >   

Because multi is specified as true, two records that match the criteria are updated.

Example 3: Change the class name of count greater than 50 to C5, set Upsert to True

Shell Code

2. > db.classes.update ({"Count": {$gt:50}},{$set: {"name":"C5"}},true,false)
4. > Db.classes.find ()
6. { "_id": ObjectId ("5030f3a3721e16c4ab180cd9"), "name": "C4", "Count": $
8. { "_id": ObjectId ("5030F3AB721E16C4AB180CDA"), "name": "C4", "Count": $
10. { "_id": ObjectId ("5030f589ce8fa8884e6cd441"), "name": "C5"}
12. >

There are no records in the collection that count is greater than 50, but because Upsert is specified as true, a new record is inserted if it is not found.

1.2save command

MongoDB Another update command is save, in the following format:

Db.collection.save (obj)

Obj represents an object that needs to be updated, and MongoDB replaces the Obj object with a record that already exists in the collection if there is already a record of "_id" that is identical to obj, and inserts the Obj object if it does not exist.

This command is relatively simple and the example is omitted.

Second, data update operator

1. $inc

Usage: {$inc: {Field:value}}

Function: Adds value to a field of a number

Example: Increase the age of the student with name Chenzhou by 5

Shell Code

2. > Db.students.find ()
4. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "name": "Chenzhou", "age":
6. #查询结果显示年龄为
8. > db.students.update ({name:"Chenzhou"},{$inc: {Age:5}})
10. #执行修改, increase the age by 5 .
12. > Db.students.find ()
14. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "name": "Chenzhou", "age": + }
16. >
18. #查询结果显示年龄为27, modified successfully

2. $set

Usage: {$set: {Field:value}}

Function: Sets the value of a field in a document

Example: Set the age of Chenzhou to 23 years

Shell Code

1. > db.students.find ()   
2. {  "_id"  : objectid ( "5030f7ac721e16c4ab180cdb"),   "name"  :  "Chenzhou",   "age"  :  27 }  
3. >  Db.students.update ({name: "Chenzhou"},{$set: {age:23}})   
4. > db.students.find ()   
5. {  "_id"  : objectid ( "5030f7ac721e16c4ab180cdb"),   "Chenzhou",  23  }  
6. >   

As you can see from the results, the age of the update changed from 27 to 23.

3. $unset

Usage: {$unset: {field:1}}

Role: Delete a field

Example: Remove the Age field for Chenzhou

Shell Code

1. > Db.students.find ()
2. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "name": "Chenzhou", "age": $
3. > db.students.update ({name:"Chenzhou"},{$unset: {Age:1}})
4. > Db.students.find ()
5. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "name": "Chenzhou"}
6. >

4. $push

Usage: {$push: {Field:value}}

Function: Append value to field. Note: field can only be an array type, and if field does not exist, an array type is automatically inserted

Example: Adding an alias "Michael" to Chenzhou

Shell Code

1. > db.students.find ()   
2. {  "_id"  : objectid ( "5030f7ac721e16c4ab180cdb"),  
3. > db.students.update ({name: "Michael"})   
4. > db.students.find ( )   
5. {  " 5030f7ac721e16c4ab180cdb "),  " Ailas " : [ " Michael " ], " name " : " Chenzhou " }  
6. >   

As you can see from the results, an array type field alias is appended to the record, and the field has a value of "Michael"

5.pushAll

Usage: {$pushAll: {Field:value_array}}

Function: Use the same as $push, except that $pushall can append multiple values to an array field at a time.

Example: Appending an alias to Chenzhou A1,A2

Shell Code

2. > Db.students.find ()
4. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "Michael"], "name": "Chenzhou"}
6. > db.students.update ({name:"Chenzhou"},{$pushAll: {"Ailas": ["A1","A2"]}})
8. > Db.students.find ()
10. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "Michael", "A1", "A2"], "name": "Chenzhou"}
12. >

6. $addToSet

Usage: {$addToSet: {Field:value}}

Function: Adds a value to the array, and only increases if the value does not exist in the array.

Example: Add two aliases to the Chenzhou name field A3, A4

Shell Code

2. > Db.students.find ()
4. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "Michael", "A1", "A2"], "name": "Chenzhou"}
6. > db.students.update ({name:"Chenzhou"},{$addToSet: {"Ailas": ["A3","A4"]}})
8. > Db.students.find ()
10. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "Michael", "A1", "A2", [ "A3", "A4"], "name": "Chenzhou"}
12. >

As can be seen from the results, after the update Ailas field more than one object, this object contains 2 data, respectively, A3, A4

7. $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

Example: Delete the first alias in the Alias field in a Chenzhou record

Shell Code

2. > Db.students.find ()
4. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "Michael", "A1", "A2", [ "A3", "A4"], "name": "Chenzhou"}
6. > db.students.update ({name:"Chenzhou"},{$pop: {"Ailas":-1}})
8. > Db.students.find ()
10. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "A1", "A2", [ "A3", "A4"]], "Name": "Chenzhou"}
12. >

By the result can read a book, the first alias Michael has been deleted.

We then use the command to delete the last alias:

Shell Code

2. > Db.students.find ()
4. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "A1", "A2", [ "A3", "A4"]], "Name": "Chenzhou"}
6. > db.students.update ({name:"Chenzhou"},{$pop: {"Ailas":1}})
8. > Db.students.find ()
10. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "A1", "A2"], "name": "Chenzhou" }  
12. >

As can be seen from the results, the last alias ["A3", "A4"] in the alias field was deleted.

8. $pull

Usage: {$pull: {Field:_value}}

Function: Removes a value equal to _value from the array field

Example: Delete an alias in a Chenzhou record A1

Shell Code

2. > Db.students.find ()
4. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "A1", "A2"], "name": "Chenzhou" }  
6. > db.students.update ({name:"Chenzhou"},{$pull: {"Ailas":"A1"}})
8. > Db.students.find ()
10. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "A2"], "name": "Chenzhou"} /c15>
12. >

9. $pullAll

Usage: {$pullAll: Value_array}

Function: Use the same as $pull, you can delete multiple values in an array at once.

Example: Delete all aliases within a Chenzhou record

Shell Code

2. > Db.students.find ()
4. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [ "A1", "A2"], "name": "Chenzhou" }  
6. > db.students.update ({name:"Chenzhou"},{$pullAll: {"Ailas": ["A1","A2"]}})
8. > Db.students.find ()
10. { "_id": ObjectId ("5030f7ac721e16c4ab180cdb"), "Ailas": [], "name": "Chenzhou"} /c1>
12. >

You can see that A1 and A2 have all been removed.

Ten. $rename

Usage: {$rename: {old_field_name:new_field_name}}

Role: Renaming a field

Example: Rename the Name field of the Chenzhou record to sname

Shell Code

1. > db.students.find ()   
2. {  "_id"  : objectid ( "5030f7ac721e16c4ab180cdb"),   "Ailas"  : [ ],  "name"  :  "Chenzhou"  }  
3. >  Db.students.update ({name: "Chenzhou"},{$rename: { "name": "Sname"}})   
4. > db.students.find ()   
5. { " _id " : objectid (" 5030f7ac721e16c4ab180cdb "),  "Ailas"  : [ ],  "sname"  :  "Chenzhou"  }  
6. >    

As a result, you can see that the Name field has been updated to sname.

MongoDB Data Update command