MongoDB Learning Note 9 Deep MongoDB Update action: modifier $inc

Ongodb Chinese file in the database after the Update method updated the document, the Update method has two parameters, such as

Update (ARGS1,ARGS2)

ARGS1 refers to the condition of querying a document;

ARGS2 refers to what changes are made to the document being queried;

$inc used to increase the value of the key used, if the key is not present to create;

$INC the key values that can only be modified must be integer, Long Integer, and double-precision floating-point types.

Use $inc to increase the key value:

> db.post.findone ({"id": 0})    {              "_id"  : objectid ("54a530c3ff0df3732bac167f"),              "id"  : 0,              "name"  :  "Joe",              "Age"  : 65,             "comments"  : {                      "1"  : 4,                      "2"  : 2,                      "3"  : 3             }    }    >  Db.post.update ({"id": 0}, {$inc: {"Age": 6}})     writeresult ({  "nmatched"  :  1,  "nupserted"  : 0,  "nmodified"  : 1 })

Results after modification:  

> db.post.findone ({"id": 0})     {              "_id"  : objectid ("54a530c3ff0df3732bac167f"),              "id"  : 0,              "name"  :  "Joe",              "Age"  : 71,             " Comments " : {                      "1"  : 4,                      "2"  : 2,                      "3"  :  3             }    } 

Use $inc to reduce key values:

> db.post.update ({"id": 0}, {$inc: {"Age": -16}}) Writeresult ({"nmatched": 1, "nupserted": 0, "nmodified": 1})

The modified result:

> db.post.findone ({"id": 0})     {              "_id"  : objectid ("54a530c3ff0df3732bac167f"),              "id"  : 0,              "name"  :  "Joe",              "Age"  : 55,             " Comments " : {                      "1"  : 4,                      "2"  : 2,                      "3"  :  3            }    }    > 

This article is from the "Margin with Wish" blog, please be sure to keep this source http://281816327.blog.51cto.com/907015/1598401

MongoDB Learning Note 9 Deep MongoDB Update action: modifier $inc