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