MongoDB Learning Note 8 Deep MongoDB update action: modifier $set

MongoDB Chinese file in the database after the Update method updates 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;

One, document replacement

> joe1= Db.post.findOne ({"Age": +}) {"_id": ObjectId ("54a530c3ff0df3732bac1680"), "id": 1, "name  ":" Joe "," Age ": 20}> joe1.age=2121> db.post.update ({" id ": 1},joe1) Writeresult ({" nmatched ": 1," nupserted " : 0, "nmodified": 1}) >

The modified result:

> joe1= Db.post.findOne ({"Age": +}) {"_id": ObjectId ("54a530c3ff0df3732bac1680"), "id": 1, "name ":" Joe "," Age ": 21}>

Second, the use of modified device

1. $set modifier

$set used to specify the value of a field that is created if the field does not exist;

> Db.post.findOne () {"_id": ObjectId ("54a530c3ff0df3732bac167f"), "id": 0, "name" : "Joe", "Age": 65}

To increase the comments key:

> db.post.update ({"id": 0}, ...    {$set: {"Comments": "I Love You"}}) Writeresult ({"nmatched": 1, "nupserted": 0, "nmodified": 1}) > Db.post.findOne () {"_id": Object ID ("54a530c3ff0df3732bac167f"), "id": 0, "name": "Joe", "Age": all, "comment S ":" I Love You "} >

To modify the value of the comments key:

> db.post.update ({"id": 0}, {$set: {"Comments": "I don ' t Love You"}}) Writeresult ({"nmatched": 1, "nupserted": 0, "NM Odified ": 1}" > Db.post.findOne () {"_id": ObjectId ("54a530c3ff0df3732bac167f"), "id": 0, "name": "Joe", "Age": All, "comments": "I don t Love You"} >

Modify the value of the comments array:

> db.post.update ({"id": 0}, {$set: {"Comments": ["i love you", "or", "I don" T love  you "]})    writeresult ({ " nmatched " : 1, " nupserted " : 0,   "Nmodified"  : 1 })     > db.post.findone ({"id": 0})      {             "_id"  :  ObjectId ("54a530c3ff0df3732bac167f"),             " ID " : 0,            " name " : " Joe ",            " "Age"  : 65,              "Comments"  : [                      "I love  you ",                     " or ",                      "I don ' T love you"              ]    }    >

To remove the value of comments:

> db.post.update ({"id": 0}, {$unset: {"Comments": 1}}) Writeresult ({"nmatched": 1, "nupserted": 0, "nmodified": 1})            > Db.post.findOne ({"id": 0}) {"_id": ObjectId ("54a530c3ff0df3732bac167f"), "id": 0, "Name": "Joe", "Age": $ >

2. Modify the inline document

> db.post.findone ({"id": 0})     {              "_id"  : objectid ("54a530c3ff0df3732bac167f"),              "id"  : 0,              "name"  :  "Joe",              "Age"  : 65,             " Comments " : {                      "1"  : 1,                      "2"  : 2,                      "3"  :  3            }    }    >  Db.post.update ({"id": 0}, {$set: {"Comments.1": 4})     writeresult ({  "nmatched"  : 1,  "nupserted"  : 0,  "nmodified"  : 1 })      > db.post.findone ({"id": 0})     {              "_id"  : objectid ("54a530c3ff0df3732bac167f"),              "id"  : 0,              "name"  :  "Joe",              "Age"  : 65,             " 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/907015/1598398

MongoDB Learning Note 8 Deep MongoDB update action: modifier $set