46 lines
1.4 KiB
Markdown
46 lines
1.4 KiB
Markdown
---
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id: xowl
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title: DynamoDB
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tags: [AWS]
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created: Sunday, June 09, 2024
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---
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# DynamoDB
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## Data structure
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### Non-relational tables
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DynamoDB is "NoSQL" because it does not support #SQL queries and is
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non-relational meaning there cannot be JOIN operations via
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[foreign_keys](Foreign_keys_in_SQL.md)
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### Primary key
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Although the data is stored as a table, one of the attributes is a primary key
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and the rest of the attributes are effectively the values associated with it.
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Because DynamoDB is schemaless, neither the attributes or their data types need
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to be defined beforehand and each item can have its own distinct attributes.
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Each item in the table is uniquely identifiable by its primary key.
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There are two types of primary key available:
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- partition key: a simple primary key composed of one attribute only. Because
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the primary key is hash-mapped items can be retrieved very rapidly using the
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primary key.
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- composite key: this comprises a partition key and a _sort key_ both of which
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are attributes
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However, you can also set one or more **secondary indices**. A secondary index
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lets you query the data in the table using an alternate key, in addition to
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queries against the primary key. DynamoDB doesn't require that you use indexes,
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but they give your applications more flexibility when querying your data.
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## Usage
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## Related notes
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