In order to retrieve a Collection object for an existing
collection stored in the database call the
getCollection()
function from a Schema
object.
If the collection does not yet exist in the database, any
subsequent call of a Collection object function throws an error;
for some of the Connectors, you can prevent that and catch the
error right at the time of Collection retrival by setting the
validateExistence
field to true and pass it
as second parameter to db.getCollection()
.
MySQL Shell JavaScript Code
Press CTRL+C to copy// Get a collection object for 'my_collection' var myColl = db.getCollection('my_collection');
MySQL Shell Python Code
Press CTRL+C to copy# Get a collection object for 'my_collection' myColl = db.get_collection('my_collection')
Node.js JavaScript Code
Press CTRL+C to copy// Get a collection object for 'my_collection' var collection = db.getCollection('my_collection');
C# Code
Press CTRL+C to copy// Get a collection object for "my_collection" var myColl = db.GetCollection("my_collection"); // Get a collection object but also ensure it exists in the database var myColl2 = db.GetCollection("my_collection", ValidateExistence: true);
Python Code
Press CTRL+C to copy# Get a collection object for 'my_collection' my_coll = my_schema.get_collection('my_collection') # Get a collection object but also ensure it exists in the database my_coll = my_schema.get_collection('my_collection', True)
Java Code
Press CTRL+C to copy// Get a collection object for 'my_collection' Collection myColl = db.getCollection("my_collection"); // Get a collection object but also ensure it exists in the database // Second parameter is: boolean requireExists Collection myColl = db.getCollection("my_collection", true);
C++ Code
Press CTRL+C to copy// Get a collection object for 'my_collection' Collection myColl = db.getCollection("my_collection"); // Get a collection object but also ensure it exists in the database Collection myColl = db.getCollection("my_collection", true);
The createCollection()
, together with the
ReuseExistingObject
field set to true, can be
used to create a new collection or reuse an existing collection
with the given name. See Section 4.2.1, “Creating a Collection”
for details.
In most cases it is good practice to create database objects during development time and refrain from creating them on the fly during the production phase of a database project. Therefore it is best to separate the code that creates the collections in the database from the actual user application code.