20.3.3.2 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. In MySQL 8.0.11 and higher, document IDs are generated by the server, not the client, so MySQL Shell does not automatically set an _id value. A MySQL server at 8.0.11 or higher sets an _id value if the document does not contain the _id field. A MySQL server at an earlier 8.0 release or at 5.7 does not set an _id value in this situation, so you must specify it explicitly. If you do not, MySQL Shell returns error 5115 Document is missing a required field. For more information see Understanding Document IDs.

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