MongoDB command example

Use the example of a book to describe how to use the mongodb command. Add a library document: db. books. insert ({name: learn more about MongoDB}); then, you can check whether the insert is successful: db. books. find (); the printed results are similar to the following: {_ id: ObjectId (4f8e8a8e7a919fd8a1a37e2d), name: Deep Learning Mo

Use the example of a book to describe how to use the mongodb command. Add a library document: db. books. insert ({name: learn more about MongoDB}); then, you can check whether the insert is successful: db. books. find (); the printed results are similar to the following: {_ id: ObjectId (4f8e8a8e7a919fd8a1a37e2d), name: Deep Learning Mo

Use the example of a book to describe how to use the mongodb command.

Add

Insert a book document:

Db. books. insert ({name: 'learn MongoDB in depth '});

Then, you can check whether the insertion is successful:

Db. books. find ();

The printed results are similar to the following:

{"_ Id": ObjectId ("4f8e8a8e7a919fd8a1a37e2d"), "name": "Learn MongoDB in depth "}

Now, you don't want this record. Delete it:

Db. books. remove ();

If you use find () Again, the content will not be printed. Note that remove () will delete all documents in the collection. How to delete a document with a specified condition will be discussed later.

Modify

Create a new library document:

Db. books. insert ({name: 'History of money ', items: []});

Here I have added an empty array, which will be useful later.

Now I want to change the book name to: learn more about MongoDB.

Command:

Db. books. update ({_ id: ObjectId ("4f8e8a8e7a919fd8a1a37e2d")}, {name: 'learn MongoDB in depth '}, false );

The disadvantage of the preceding command is that the items attribute is missing. If you only want to modify the name of a book without affecting other attributes of the document, you can do this:

Db. books. update ({_ id: ObjectId ("4f8ea9a619bc948142e0dad5") },{$ set: {name: 'Deep in MongoDB '}}, false );

Now, I want to add something to an empty array, for example, an entry:

{_ Id: ObjectId, type: 'Chapter ', items: []}

The command is as follows:

? Db. books. update ({_ id: ObjectId ('4f8ea9a619bc948142e0dad5')}, {$ push: {items: {_ id: new ObjectId (), type: 'Chapter ', items: [] }}, false );

Let's take a look at the result:

{
"_ Id": ObjectId ("4f8ea9a619bc948142e0dad5 ″),
"Items ":[
{
"_ Id": ObjectId ("4f8eaf227a919fd8a1a37e2e "),
"Type": "chapter ",
"Items": []
}
],
"Name": "wild food"
}

Now we want to add content to the array of entries in 4f8eaf227a919fd8a1a37e2e. How can we do this? To use push, you can append an element to the specified array:

Db. books. update ({_ id: ObjectId ('4f8ea9a619bc948142e0dad5')}, {$ push: {items: {_ id: new ObjectId (), type: 'Chapter ', items: [] }}, false );

Now I find that the type value of the appended element is incorrect. I want to change it to section:

Db. books. update ({_ id: ObjectId ("4f8ea9a619bc948142e0dad5"), 'items. _ id': ObjectId ("4f8ef10b7a919fd8a1a37e32")}, {$ set: {'items. $. type ': 'region'}, false );

Can I append an element to the items array of the items element? The answer is yes:

Db. books. update ({_ id: ObjectId ("4f8ea9a619bc948142e0dad5"), 'items. _ id': ObjectId ("4f8ef10b7a919fd8a1a37e32")}, {$ push: {'items. $. items ': {_ id: new ObjectId (), type: 'core', items: [] }}, false );

The append result is similar to the following:

{
"_ Id": ObjectId ("4f8ea9a619bc948142e0dad5 ″),
"Items ":[
{
"_ Id": ObjectId ("4f8ef10b7a919fd8a1a37e32 "),
"Items ":[
{
"_ Id": ObjectId ("4f8ef4d17a919fd8a1a37e33 "),
"Type": "section ",
"Items": []
}
],
"Type": "chapter"
}
]
}

Delete

If you want to delete an attribute that is not added to the document, for example:

Db. books. update ({_ id: ObjectId ('4f8e8a8e7a919fd8a1a37e2d ')}, {$ push: {hello: 'test1' }}, false );

Adds a useless attribute for the document, he l lo, which is an array.

Delete it:

Db. books. update ({_ id: ObjectId ('4f8e8a8e7a919fd8a1a37e2d ') },{$ unset: {hello: 1 }}, false );

Original article address: MongoDB command usage example. Thank you for sharing it.