19.Delete Documents-官方文档摘录

1 插入例子

db.inventory.insertMany( [

   { item: "journal", qty: 25, size: { h: 14, w: 21, uom: "cm" }, status: "A" },

   { item: "notebook", qty: 50, size: { h: 8.5, w: 11, uom: "in" }, status: "P" },

   { item: "paper", qty: 100, size: { h: 8.5, w: 11, uom: "in" }, status: "D" },

   { item: "planner", qty: 75, size: { h: 22.85, w: 30, uom: "cm" }, status: "D" },

   { item: "postcard", qty: 45, size: { h: 10, w: 15.25, uom: "cm" }, status: "A" },

]);

2 删除所有

db.inventory.deleteMany({})

3 删除匹配的行

db.inventory.deleteMany({ status : "A" })

4 删除最多一行记录

db.inventory.deleteOne( { status: "D" } )

5 注意

1.删除对应元素并不会删除对应的索引

2.删除具有原子性

This page provides examples of delete operations using the following methods in the mongo shell:

The examples on this page use the inventory collection. To populate the inventory collection, run the following:

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db.inventory.insertMany( [

   { item: "journal", qty: 25, size: { h: 14, w: 21, uom: "cm" }, status: "A" },

   { item: "notebook", qty: 50, size: { h: 8.5, w: 11, uom: "in" }, status: "P" },

   { item: "paper", qty: 100, size: { h: 8.5, w: 11, uom: "in" }, status: "D" },

   { item: "planner", qty: 75, size: { h: 22.85, w: 30, uom: "cm" }, status: "D" },

   { item: "postcard", qty: 45, size: { h: 10, w: 15.25, uom: "cm" }, status: "A" },

]);

You can run the operation in the web shell below:

Delete All Documents

To remove all documents from a collection, pass an empty filter document {} to thedb.collection.deleteMany() method.

The following example deletes all documents from the inventory collection:

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db.inventory.deleteMany({})

The method returns a document with the status of the operation. For more information and examples, seedeleteMany().

Delete All Documents that Match a Condition

You can specify criteria, or filters, that identify the documents to delete. The filters use the same syntax as read operations.

To specify equality conditions, use <field>:<value> expressions in the query filter document:

{ <field1>: <value1>, ... }

A query filter document can use the query operators to specify conditions in the following form:

{ <field1>: { <operator1>: <value1> }, ... }

To delete all documents that match a deletion criteria, pass a filter parameter to the deleteMany() method.

The following example removes all documents from the inventory collection where the status field equals"A":

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db.inventory.deleteMany({ status : "A" })

The method returns a document with the status of the operation. For more information and examples, seedeleteMany().

Remove Only One Document that Matches a Condition

To delete at most a single document that matches a specified filter (even though multiple documents may match the specified filter) use the db.collection.deleteOne() method.

The following example deletes the first document where status is "D".

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db.inventory.deleteOne( { status: "D" } )

Delete Behavior

Indexes

Delete operations do not drop indexes, even if deleting all documents from a collection.

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.