MongoDB Quick Start

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Database operations are generally crud, the most difficult of which is the query, all of us first to understand the MongoDB

Inserting (insert)

When it comes to insertions, we have to talk about how to create a database, how to create a collection, and then how to create a document.

The set mentioned here is the table in the relational database, and the document is (Row).

Now all we have to do is create a flast database, create a M collection, and insert a document.

　　　　

Updates (update)

Let's start with a simple update:

We now want to name: "Xu" into name: "Joe", age:23

We can see the three properties shown in the Red box

　　　　　　nmatched: Represents the number of captures

　　　　　　nupserted: Represents the number of insertions

　　　　　　nmodified: Represents the number of modifications

Now let's look at the real syntax of update

Db.collection.update (<Query>,   <Update>, {upsert:<Boolean>, (false) whether to insert multi when it does not exist:<Boolean>, (false) whether to select multiple Writeconcern:<Document>exception level})

To demonstrate the above three optional parameters and explain the updated parameters, we need to add a document

　　

Demonstration of the first Upsert (false)

　　

Demonstration of the second multi (false)

The following code is then available:

　　

From the above we can also see the capture of two, modified two,

We can also use the findandmodify command to modify

With this command we can clearly see which documents have been modified and of course not recommended, loss performance

　　By the way, what are the commands for "findandmodify":

> Query statement

> UPDATE statement to update only the first statement found

> Remove (Boolean) is removed

>New (Boolean) represents whether to return to the pre-update or post-update, the default is the pre-update, from the above value can be seen

　　　　　　　　

Delete Remove

Delete Of course is relatively simple now, look directly at the grammar bar!

Db.collection.remove (<Query>,(optional) Delete the condition of the document {justone:<Boolean>,(optional) If set to TRUE or 1, only one document is deleted. Writeconcern:<Document>(optional) the level at which the exception is thrown.    })

Take a look at the example

QueryFind

　　Queries are generally the hardest part, because there are a lot of logic that we learn from the simplest:

For example, we want to query the Name= "Jack" document.

Can see that we have nothing to find, but I believe that with the above changes to this must be understandable,

Our focus is to understand the $ directive

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MongoDB Quick Start