View source for User-Defined Function (UDF)

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'''Category:''' Server-Side Programming

'''Summary:''' Read-only JavaScript function extending SQL queries with custom computations.

== Overview ==
A user-defined function (UDF) is server-side JavaScript logic in Azure Cosmos DB for NoSQL that extends the SQL query language with custom scalar computations (e.g., custom string formatting or calculations), callable from within a SQL query. Unlike stored procedures and triggers, UDFs are read-only and cannot modify data.

''[Image: udf.png (User-Defined Function)]''

== More Info & Links ==
* [https://learn.microsoft.com/en-us/azure/cosmos-db/nosql/how-to-write-stored-procedures-triggers-udfs#udfs Microsoft Learn: How to write user-defined functions]

== DP-420 Style Practice Questions ==
'''Q1.''' What is the primary purpose of a user-defined function (UDF) in Azure Cosmos DB for NoSQL?
* A. Extending SQL queries with custom, read-only scalar computations
* B. Performing multi-item transactional writes
* C. Automatically triggering on every item creation
* D. Managing container-level throughput

'''Q2.''' Can a UDF modify data in Azure Cosmos DB?
* A. No, UDFs are read-only and cannot modify data
* B. Yes, UDFs can perform inserts, updates, and deletes
* C. Only if invoked from a stored procedure
* D. Only for items within the same partition

== Answer Key ==
''Answers are listed at the very end so you can attempt the questions first.''

* '''Q1 (User-Defined Function (UDF)):''' A. Extending SQL queries with custom, read-only scalar computations — UDFs add custom computational logic callable from SQL queries, but unlike stored procedures/triggers, they cannot write data.
* '''Q2 (User-Defined Function (UDF)):''' A. No, UDFs are read-only and cannot modify data — UDFs are restricted to read-only scalar computation and cannot write or modify data.

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''DP-420: Designing and Implementing Cloud-Native Applications Using Microsoft Azure Cosmos DB — term detail page''

[[Category:DP-420 Terminology]]
[[Category:Server-Side Programming]]