Short for foreign key: a column pointing at the primary key of a different table. Azure Databricks treats both key constraint types as information only and does not enforce them.
Also called foreign key.
Read more: Microsoft Learn
In the Ultra Transcenders books
Each book explains FK in context, with comparison tables and the common traps.
Terms in this definition
- Primary key
Uniquely identifies every row in a relational table, using one column or several together. A foreign key in another table holds this value to reference the row.
- Event
Table in Log Analytics where entries from Windows event logs are kept.
- Databricks
Analytics platform built on Apache Spark where data is processed in notebooks; Unity Catalog is the governance model it recommends.
- Index field attributes
Settings applied to each field in an Azure AI Search index:
searchablefor full text,retrievableto return it,filterablefor exact-match$filter,sortable,facetablefor counts, andkeyfor the unique document ID.
Related terms
- CASCADE
With
ON DELETE CASCADEorON UPDATE CASCADEon a foreign key, changing a referenced key also deletes or updates the rows that point to it. Without it, the defaultNO ACTIONcauses the change to fail. - Composite key
A primary or foreign key that needs two or more columns together to be unique, for example an order number combined with an item number to identify each line of an order.
- JOIN
Combines rows from two or more tables in one SELECT, most often by pairing a primary key with the foreign key that refers to it.
- NOCHECK
Using WITH NOCHECK, a CHECK or foreign key constraint can be created or switched back on without the existing data being validated. It then counts as untrusted, and query optimisation ignores it until you enable it again WITH CHECK.
- RDBMS
Relational database management system. This software runs the database and can normally enforce referential integrity, so that an unmatched foreign key value (one pointing to no existing primary key) is refused.
- Referential integrity
A guarantee, upheld by foreign key constraints in a relational database management system, that no foreign key refers to a missing row; any change that would break such a link is refused.