markdown MongoDB备忘单
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# MongoDB Cheat Sheet
## Show All Databases
```
show dbs
```
## Show Current Database
```
db
```
## Create Or Switch Database
```
use acme
```
## Drop
```
db.dropDatabase()
```
## Create Collection
```
db.createCollection('posts')
```
## Show Collections
```
show collections
```
## Insert Row
```
db.posts.insert({
title: 'Post One',
body: 'Body of post one',
category: 'News',
tags: ['news', 'events'],
user: {
name: 'John Doe',
status: 'author'
},
date: Date()
})
```
## Insert Multiple Rows
```
db.posts.insertMany([
{
title: 'Post Two',
body: 'Body of post two',
category: 'Technology',
date: Date()
},
{
title: 'Post Three',
body: 'Body of post three',
category: 'News',
date: Date()
},
{
title: 'Post Four',
body: 'Body of post three',
category: 'Entertainment',
date: Date()
}
])
```
## Get All Rows
```
db.posts.find()
```
## Get All Rows Formatted
```
db.find().pretty()
```
## Find Rows
```
db.posts.find({ category: 'News' })
```
## Sort Rows
```
# asc
db.posts.find().sort({ title: 1 }).pretty()
# desc
db.posts.find().sort({ title: -1 }).pretty()
```
## Count Rows
```
db.posts.find().count()
db.posts.find({ category: 'news' }).count()
```
## Limit Rows
```
db.posts.find().limit(2).pretty()
```
## Chaining
```
db.posts.find().limit(2).sort({ title: 1 }).pretty()
```
## Foreach
```
db.posts.find().forEach(function(doc) {
print("Blog Post: " + doc.title)
})
```
## Find One Row
```
db.posts.findOne({ category: 'News' })
```
## Find Specific Fields
```
db.posts.find({ title: 'Post One' }, {
title: 1,
author: 1
})
```
## Update Row
```
db.posts.update({ title: 'Post Two' },
{
title: 'Post Two',
body: 'New body for post 2',
date: Date()
},
{
upsert: true
})
```
## Update Specific Field
```
db.posts.update({ title: 'Post Two' },
{
$set: {
body: 'Body for post 2',
category: 'Technology'
}
})
```
## Increment Field (\$inc)
```
db.posts.update({ title: 'Post Two' },
{
$inc: {
likes: 5
}
})
```
## Rename Field
```
db.posts.update({ title: 'Post Two' },
{
$rename: {
likes: 'views'
}
})
```
## Delete Row
```
db.posts.remove({ title: 'Post Four' })
```
## Sub-Documents
```
db.posts.update({ title: 'Post One' },
{
$set: {
comments: [
{
body: 'Comment One',
user: 'Mary Williams',
date: Date()
},
{
body: 'Comment Two',
user: 'Harry White',
date: Date()
}
]
}
})
```
## Find By Element in Array (\$elemMatch)
```
db.posts.find({
comments: {
$elemMatch: {
author: 'Mary Williams'
}
}
}
)
```
## Add Index
```
db.posts.createIndex({ title: 'text' })
```
## Text Search
```
db.posts.find({
$text: {
$search: "\"Post O\""
}
})
```
## Greater & Less Than
```
db.posts.find({ views: { $gt: 2 } })
db.posts.find({ views: { $gte: 7 } })
db.posts.find({ views: { $lt: 7 } })
db.posts.find({ views: { $lte: 7 } })
```
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