Amazon DynamoDB Concepts
External
Internal
Overview
Amazon DynamoDB is a managed NoSQL database service.
Table
A table is a collection of items. A table contains zero or more items. An item is a group of attributes that is uniquely identifiable among all other items. Items are similar in many ways to rows, records or tuples in other database systems. There is no limit to the number of items that can be stored in a table.
When a table is created, its primary key must be specified. Other than the primary key, tables do not have schemas, which means that neither the attributes nor their data types need to be defined beforehand.
Item
An item is a collection of attributes. Each item can have its own distinct attributes.
Primary Key
DynamoDB uses primary keys to uniquely identify each item in a table. There are two types of primary keys:
Partition Key
A simple primary key defined by one attribute. In a table that has only a partition key, no two items can have the same partition key value. DynamoDB uses the partition key's value as input to an internal hash function. The output from the hash function determines the partition (physical storage internal to DynamoDB) in which the item will be stored.
Partition Key and Sort Key
A primary key may be composite, in that it is defined by two attributes: the partition key and the sort key.
Attribute
An attribute is a fundamental data element, something that does not need to be broken down any further.
Attribute Types
Scalar
Number
String
Nested Attributes
DynamoDB supports nested attributes up 32 levels deep.