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22.3.3.2 Working with Collections

To work with the collections in a schema, use the db global object to access the current schema. In this example we are using the world_x schema imported previously, and the countryinfo collection. Therefore, the format of the operations you issue is db.collection_name.operation, where collection_name is the name of the collection which the operation is executed against. In the following examples, the operations are executed against the countryinfo collection.

Add a Document

Use the add() method to insert one document or a list of documents into an existing collection. Insert the following document into the countryinfo collection. As this is multi-line content, press Enter twice to insert the document.

mysql-js> db.countryinfo.add(
 {
    GNP: .6,
    IndepYear: 1967,
    Name: "Sealand",
    Code: "SEA",
    demographics: {
        LifeExpectancy: 79,
        Population: 27
    },
    geography: {
        Continent: "Europe",
        Region: "British Islands",
        SurfaceArea: 193
    },
    government: {
        GovernmentForm: "Monarchy",
        HeadOfState: "Michael Bates"
    }
  }
)

The method returns the status of the operation. You can verify the operation by searching for the document. For example:

mysql-js> db.countryinfo.find("Name = 'Sealand'")
{
    "GNP": 0.6,
    "_id": "00005e2ff4af00000000000000f4",
    "Name": "Sealand",
    "Code:": "SEA",
    "IndepYear": 1967,
    "geography": {
        "Region": "British Islands",
        "Continent": "Europe",
        "SurfaceArea": 193
    },
    "government": {
        "HeadOfState": "Michael Bates",
        "GovernmentForm": "Monarchy"
    },
    "demographics": {
        "Population": 27,
        "LifeExpectancy": 79
    }
}

Note that in addition to the fields specified when the document was added, there is one more field, the _id. Each document requires an identifier field called _id. The value of the _id field must be unique among all documents in the same collection. Document IDs are generated by the server, not the client, so MySQL Shell does not automatically set an _id value. MySQL sets an _id value if the document does not contain the _id field. For more information, see Understanding Document IDs.

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