笔记-mongodb数据操作
1. 数据操作
1.1. 插入
db.COLLECTION_NAME.insert(document)
案例：
db.inventory.insertOne(
{ item: "canvas", qty: 100, tags: ["cotton"], size: { h: 28, w: 35.5, uom: "cm" } }
)
如果该集合不在该数据库中， MongoDB 会自动创建该集合并插入文档；
返回一个field，就是它在数据库中的样子。
{ "_id" : ObjectId("5cd25bc779076536c9113317"), "item" : "canvas", "qty" : 100,
"tags" : [ "cotton" ], "size" : { "h" : 28, "w" : 35.5, "uom" : "cm" } }
一次插入多条记录
db.inventory.insertMany([
{ item: "journal", qty: 25, tags: ["blank", "red"], size: { h: 14, w: 21, uom: "cm" } },
{ item: "mat", qty: 85, tags: ["gray"], size: { h: 27.9, w: 35.5, uom: "cm" } },
{ item: "mousepad", qty: 25, tags: ["gel", "blue"], size: { h: 19, w: 22.85, uom: "cm" } }
])
返回结果如下：
{
"acknowledged" : true,
"insertedIds" : [
ObjectId("5cd25cbd79076536c9113318"),
ObjectId("5cd25cbd79076536c9113319"),
ObjectId("5cd25cbd79076536c911331a")
]
}
1.1.1. insert behavior
如果集合不存在，插入操作会自动创建集合。
_id Field
In MongoDB, each document stored in a collection requires a unique _id field that acts as a primary key. If an inserted document omits the _id field, the MongoDB driver automatically generates an ObjectId for the _idfield.
This also applies to documents inserted through update operations with upsert: true.
集合中的每个文档都必需有一个_id域作为主键。如果插入时没有指定，mongodb自动生成一个Objectid
Atomicity
All write operations in MongoDB are atomic on the level of a single document. For more information on MongoDB and atomicity, see Atomicity and Transactions
对于单个document而言，所有的写操作都是原子化的。
When a single write operation (e.g. db.collection.updateMany()) modifies multiple documents, the modification of each document is atomic, but the operation as a whole is not atomic.
对于集合则不然。
1.2. 查询
1.2.1. find()
MongoDB 查询文档使用 find()，它以非结构化的方式来显示所有文档。
db.collection.find(query, projection)
query ：可选，使用查询操作符指定查询条件
projection ：可选，使用投影操作符指定返回的键。查询时返回文档中所有键值， 只需省略该参数即可（默认省略）。
如果你需要以易读的方式来读取数据，可以使用 pretty() 方法，语法格式如下：
>db.col.find().pretty()
pretty() 方法以格式化的方式来显示所有文档。
findOne()：只返回第一个满足条件的文档。
The db.collection.find() method returns a cursor to the matching documents.
它返回一个cursor
MongoDB 与 RDBMS的等效 Where 子句
要在一些条件的基础上查询文档，可以使用以下条件语句。
| oper |
语法 |
示例 |
等效语句 |
| = |
{<key>:<value>} |
db.mycol.find({"by":"yiibai"}).pretty() |
where by = 'yiibai' |
| < |
{<key>:{$lt:<value>}} |
db.mycol.find({"likes":{$lt:50}}).pretty() |
where likes < 50 |
| <= |
{<key>:{$lte:<value>}} |
db.mycol.find({"likes":{$lte:50}}).pretty() |
where likes <= 50 |
| > |
{<key>:{$gt:<value>}} |
db.mycol.find({"likes":{$gt:50}}).pretty() |
where likes > 50 |
| >= |
{<key>:{$gte:<value>}} |
db.mycol.find({"likes":{$gte:50}}).pretty() |
where likes >= 50 |
| != |
{<key>:{$ne:<value>}} |
db.mycol.find({"likes":{$ne:50}}).pretty() |
where likes != 50 |
db.inventory.find( {} ) # 返回所有document，等效于slect * from table;
1.2.2. 条件查询
db.inventory.find( { status: "D" } )等效于SELECT * FROM inventory WHERE status = "D"
db.inventory.find( { status: { $in: [ "A", "D" ] } } ) 等效于SELECT * FROM inventory WHERE status in ("A", "D")
db.inventory.find( { status: "A", qty: { $lt: 30 } } )等效于SELECT * FROM inventory WHERE status = "A" AND qty < 30
db.inventory.find( { $or: [ { status: "A" }, { qty: { $lt: 30 } } ] } )等效于SELECT * FROM inventory WHERE status = "A" OR qty < 30
db.inventory.find( {
status: "A",
$or: [ { qty: { $lt: 30 } }, { item: /^p/ } ]
} )等效于SELECT * FROM inventory WHERE status = "A" AND ( qty < 30 OR item LIKE "p%")
还有一些对于嵌套/队列/位/的查询操作方法，太细了，以后用到再写。
1.2.3. projection投影
投影是指选择返回的字段。类似于select col_name1,…. from table;
在projection参数中，0代表隐藏，1代表显示。
db.inventory.find( { status: "A" }, { item: 1, status: 1 } )等效于
SELECT _id, item, status from inventory WHERE status = "A"
如果不想显示_id，需要显示声明参数：
db.inventory.find( { status: "A" }, { item: 1, status: 1, _id: 0 } )
上面都是正向选择，下面是反向排除，就是除了声明列，其它都显示：
db.inventory.find( { status: "A" }, { status: 0, instock: 0 } )
1.3. 更新
This page uses the following mongo shell methods:
db.collection.updateOne(<filter>, <update>, <options>)
db.collection.updateMany(<filter>, <update>, <options>)
db.collection.replaceOne(<filter>, <update>, <options>)
1.3.1. updateone()
db.inventory.updateOne(
{ item: "paper" },
{
$set: { "size.uom": "cm", status: "P" },
$currentDate: { lastModified: true }
}
)
释义：
使用$set操作符更新 size.uom field to "cm" and the value of the statusfield to "P",
使用$currentDate 操作符更新 lastModified field的值；如果该域不存在，操作符会自动创建。
1.3.2. updatemany()
db.inventory.updateMany(
{ "qty": { $lt: 50 } },
{
$set: { "size.uom": "in", status: "P" },
$currentDate: { lastModified: true }
}
)
释义：
更新所有qry小于50的文档的指定域。
1.3.3. replaceone
将指定文档的内容整体更换掉，除了_id域。
db.inventory.replaceOne(
{ item: "paper" },
{ item: "paper", instock: [ { warehouse: "A", qty: 60 }, { warehouse: "B", qty: 40 } ] }
)
1.3.4. behavior
Atomicity
All write operations in MongoDB are atomic on the level of a single document. For more information on MongoDB and atomicity, see Atomicity and Transactions.
原子性，对于文档是原子化的。
_id Field
Once set, you cannot update the value of the _id field nor can you replace an existing document with a replacement document that has a different _id field value.
一旦设定，_id域是不能理发的
Document Size
For the deprecated MMAPv1, when performing update operations that increase the document size beyond the allocated space for that document, the update operation relocates the document on disk.
简单来说，如果超出指定大小，会重定位（不确定是整个文档重写然后定位还是拆分文档的域）。
Field Order
MongoDB preserves the order of the document fields following write operations except for the following cases:
The _id field is always the first field in the document.
Updates that include renaming of field names may result in the reordering of fields in the document.
Changed in version 2.6: Starting in version 2.6, MongoDB actively attempts to preserve the field order in a document. Before version 2.6, MongoDB did not actively preserve the order of the fields in a document.
Upsert Option
If updateOne(), updateMany(), or replaceOne() includes upsert : true and no documents match the specified filter, then the operation creates a new document and inserts it. If there are matching documents, then the operation modifies or replaces the matching document or documents.
For details on the new document created, see the individual reference pages for the methods.
Write Acknowledgement
With write concerns, you can specify the level of acknowledgement requested from MongoDB for write operations. For details, see Write Concern.
1.3.5. 其它方法
| Updates at most a single document that match a specified filter even though multiple documents may match the specified filter. New in version 3.2. |
|
| Update all documents that match a specified filter. New in version 3.2. |
|
| Replaces at most a single document that match a specified filter even though multiple documents may match the specified filter. New in version 3.2. |
|
| Either updates or replaces a single document that match a specified filter or updates all documents that match a specified filter. By default, the db.collection.update() method updates a single document. To update multiple documents, use the multi option. |
Additional Methods
The following methods can also update documents from a collection:
db.collection.findOneAndReplace().
db.collection.findOneAndUpdate().
db.collection.findAndModify().
1.4. 删除
方法：
实验：
查看当前文档内容
db.inventory.find({},{status:1})
单条删除
The following example deletes the first document where status is "D":
db.inventory.deleteOne( { status: "D" } )
多条删除
> db.inventory.deleteMany( { status: "D" } )
{ "acknowledged" : true, "deletedCount" : 5 }
结果是删除5个文档
db.inventory.deleteMany({}) #删除所有文档
1.4.1. behavior
Indexes
Delete operations do not drop indexes, even if deleting all documents from a collection.
删除操作不会删除索引，即使删除所有文档也是如此。
Atomicity
All write operations in MongoDB are atomic on the level of a single document. For more information on MongoDB and atomicity, see Atomicity and Transactions.
Write Acknowledgement
With write concerns, you can specify the level of acknowledgement requested from MongoDB for write operations. For details, see Write Concern.
1.5. 批量写bulk write operations
try {
db.characters.bulkWrite(
[
{ insertOne :
{
"document" :
{
"_id" : 4, "char" : "Dithras", "class" : "barbarian", "lvl" : 4
}
}
},
{ insertOne :
{
"document" :
{
"_id" : 5, "char" : "Taeln", "class" : "fighter", "lvl" : 3
}
}
},
{ updateOne :
{
"filter" : { "char" : "Eldon" },
"update" : { $set : { "status" : "Critical Injury" } }
}
},
{ deleteOne :
{ "filter" : { "char" : "Brisbane"} }
},
{ replaceOne :
{
"filter" : { "char" : "Meldane" },
"replacement" : { "char" : "Tanys", "class" : "oracle", "lvl" : 4 }
}
}
]
);
}
catch (e) {
print(e);
}
特性多了也头晕，不知道哪一种更合适，用的多了程序复杂性又高。。。。。