This is the 15th day of my participation in Gwen Challenge

1. All available databases are displayed

> show dbs;
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This command will display all of mongo’s database names and list them.

2. Switch databases

> use mydb;
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This command selects a specified database or creates one automatically if one does not exist. Note, however, that the database has no data at this time, so when you run the show DBS command, you cannot see the database. It is visible only after the dataset has been inserted.

3. Display the data set

> show collections;
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This command displays the dataset under the currently selected database. Note that if there is no data set, nothing is displayed.

4. Insert data

Insert data in the format db.{dataset name}. Insert ({data key value pair}), returns the number of inserts on success.

> db.test.insert({"name": "Island code farmer"});
WriteResult({ "nInserted": 1})Copy the code

Inserte multiple rows of data using brackets, and the result of the batch operation is returned, where nInserted returns the number of successful inserts.

> db.test.insert([{"name": "Island code farmer"}, {"name": "Nuggets"}]);
BulkWriteResult({
	"writeErrors": []."writeConcernErrors": []."nInserted": 2."nUpserted": 0."nMatched": 0."nModified": 0."nRemoved": 0."upserted": []})Copy the code

5. Update data

The command to update a data is as follows, in the format of db.{dataset name}. Update ({query condition}, {$set: {updated data}}).

> db.test.update({"name": "Island code farmer"}, {$set: {"name": "Farmers"}});
WriteResult({ "nMatched" : 1, "nUpserted": 0."nModified": 1})Copy the code

The preceding command updates only one matching data. If you want to update multiple data sets, add the following parameter: {multi: true}.

> db.test.update({"name": "Island code farmer"}, {$set: {"name": "Farmers"}}, {multi: true});
WriteResult({ "nMatched": 2."nUpserted": 0."nModified": 2})Copy the code

Multiple updates can also be made using updateMany.

> db.test.updateMany({"name": "Farmers"}, {$set: {"name": "Island code farmer"}});
{ "acknowledged" : true."matchedCount": 3."modifiedCount": 3}Copy the code

6. Replace documents

Replacing a document replaces an existing document with a new document in the format db.{dataset name}.save({new document data}). For example, the following example replaces the file whose id is 60c8a50ADB9890BF41255FE4.

> db.test.save({"_id": "60c8a50adb9890bf41255fe4"."name": "Island Moron-1"});
WriteResult({
	"nMatched": 0."nUpserted" : 1,
	"nModified": 0."_id" : "60c8a50adb9890bf41255fe4"
})
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7. Query data

The command to query data is in the format db.{dataset name}.find(). If you want to limit the number of entries, you can add limit(n).

> db.test.find();
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Query out of the format need to beautify, add pretty() can be.

> db.test.find().pretty();
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When querying by condition, add a filter parameter to find.

> db.test.find({"name":"Island code farmer"}).pretty();
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8. Count the items

Use the count() function for statistics, or pass a filter in the find method if you need to filter.

> db.test.find().count();
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9. Delete the document

Delete the document in db.test.remove({filter criteria}) format;

> db.test.remove({"name":"Island Moron-1"});
WriteResult({ "nRemoved": 1})Copy the code

The deleteOne method is used to deleteOne item, and the deleteMany method is used to delete multiple items.

> db.test.deleteOne({"name":"Island code farmer"});
{ "acknowledged" : true."deletedCount" : 1 }

> db.test.deleteMany({"name":"Island code farmer"});
{ "acknowledged" : true."deletedCount"2} :Copy the code

10. Check the help documentation

For some commands that do not understand the operation, check the operation document, the command format is db.{dataset name}.help().