Composite key

As explained in Kafka Streams in Action, Second Edition

A composite key is a record or row identifier formed from multiple fields.

How Kafka Streams in Action, Second Edition covers it

How deep it goes

Explains grouping, key-format failure, JSON configuration, and copying key fields into values.

Examples

Uses first name, last name, and activity to calculate per-person activity leaders from fitness events.

What it assumes

Assumes Kafka key-value records and aggregation basics while demonstrating multi-column grouping from a streaming schema.

What you can do after

Apply it via ksqlDB by selecting a schema-supporting key format and grouping on every field defining aggregate uniqueness.

How it connects

Connects composite keys with aggregation, GROUP BY, Kafka key-value records, JSON, and AS_VALUE.

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Also explained in

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  100 SQL Server Mistakes and How to Avoid ThemA composite key is a key whose identity is formed from multiple columns.
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  The Well-Grounded Data AnalystA composite primary key is a record key whose uniqueness is determined by a combination of multiple columns.
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  Java Persistence with Spring Data and Hibernate epubA key formed from multiple attributes or columns that jointly identify a persistent entity or relational row.
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  The Art of CodeA composite key is a key formed from multiple values that together identify an item or entry.
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  Building Web APIs with ASP.NET CoreA composite primary key is a primary key formed from multiple columns whose combined values uniquely identify a record.
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  ScyllaDB in ActionA composite primary key is a primary key formed from multiple columns whose combined values identify a row.
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  PostgreSQL Mistakes and How to Avoid ThemA composite unique key is a uniqueness rule defined over multiple columns whose combined values identify a row combination.

Compare how 8 books explain composite key →

Related concepts

• primary keykind of · A primary key is a designated column or attribute, or combination of them, that uniquely identifies each row or item in a table or data store.
• dependent entityused by · A dependent entity is an entity whose identification or existence depends on a related owner entity and cannot be fully determined independently.
• surrogate keyalternative to · A surrogate key is an artificially assigned, domain-independent identifier used to uniquely identify a database record independently of its business attributes.
• keykind of · A key is an identifier or value used to locate or access an associated entry or property in a keyed data structure.
• database tablepart of · A database table is a relational database structure that organizes records into rows and defined columns.
• k-d treeused by · A k-d tree is a binary space-partitioning tree that organizes points in multidimensional space by recursively comparing coordinate dimensions.

This explainer was generated by Manning's knowledge graph from the text of Kafka Streams in Action, Second Edition. The section links point to the parts of the book it draws on.