MongoDB Update Documentation

Update () method

The update () method is used to update a document that already exists. The syntax format is as follows:

Db.collection.update (
<query>,
<update>,
{
Upsert: <boolean>
Multi: <boolean>
Writeconcern: <document>
}
)


Parameter description:
The query:update query condition, similar to that in SQL Update query, is behind.
Update:update objects and some updated operators (such as $, $inc ... ) can also be understood as the SQL update query within the set after the
Upsert: Optional, this parameter means that if there is no record of update, insert objnew,true as INSERT, default is False, do not insert.
Multi: Optional, mongodb default is False, only update the first record found, if this parameter is true, will be found on the condition of a number of records update all.
Writeconcern: Optional, throws an exception level.


Instance

We insert the following data in the collection MyCol:

Db.mycol.insert ({"_id": +, "name": "Liang", "title": "MongoDB Overview"})
Db.mycol.insert ({"_id": 101, "name": "Guo", "title": "MongoDB Guide"})
Db.mycol.insert ({"_id": 102, "name": "June", "title": "NoSQL Database"})
Db.mycol.insert ({"_id": 104, "name": "Liuzhou", "title": "Python Quick Guide"})

Update the title with the update () method:
Db.mycol.update ({"Name": "Liang"},{$set: {"title": "MongoDB Overview2"}})

Db.mycol.find ();
{"_id": +, "name": "Liang", "title": "MongoDB Overview2"}
{"_id": 101, "name": "Guo", "title": "MongoDB Guide"}
{"_id": 102, "name": "June", "title": "NoSQL Database"}
{"_id": 104, "name": "Liuzhou", "title": "Python Quick Guide"}


The above statement only modifies the first found document, and if you want to modify multiple identical documents, you need to set the multi parameter to True.


Db.mycol2.insert ({"_id": +, "name": "Liang", "title": "MongoDB Overview"})
Db.mycol2.insert ({"_id": 101, "name": "Liang", "title": "MongoDB Guide"})
Db.mycol2.insert ({"_id": 102, "name": "Liang", "title": "NoSQL Database"})
Db.mycol2.insert ({"_id": 104, "name": "Liang", "title": "Python Quick Guide"})

Db.mycol2.update ({' name ': ' Liang '},{$set: {' title ': ' MongoDB '}},{multi:true})

Db.mycol2.find ();
{"_id": +, "name": "Liang", "title": "MongoDB"}
{"_id": 101, "name": "Liang", "title": "MongoDB"}
{"_id": 102, "name": "Liang", "title": "MongoDB"}
{"_id": 104, "name": "Liang", "title": "MongoDB"}


Save () method

The Save () method replaces an existing document with an incoming document. The syntax format is as follows:

Db.collection.save (
<document>,
{
Writeconcern: <document>
}
)

Db.mycol3.insert ({"_id": +, "name": "Liang", "title": "MongoDB"})

Db.mycol3.save ({"_id": +, "name": "Liang2", "title": "MongoDB2"})


Db.mycol3.find ()
{"_id": +, "name": "Liang2", "title": "MongoDB2"}


more examples

Update only the first record:
Db.col.update ({"Count": {$gt: 1}}, {$set: {"test2": "OK"}});

Update all:
Db.col.update ({"Count": {$gt: 3}}, {$set: {"test2": "OK"}},false,true);

Add only the first article:
Db.col.update ({"Count": {$gt: 4}}, {$set: {"Test5": "OK"}},true,false);

Add in all:
Db.col.update ({"Count": {$gt: 5}}, {$set: {"Test5": "OK"}},true,true);

Update all:
Db.col.update ({"Count": {$gt: $}}, {$inc: {"Count": 1}},false,true);

Update only the first record:
Db.col.update ({"Count": {$gt: Ten}}, {$inc: {"Count": 1}},false,false);

MongoDB Update Documentation