CREATE FUNCTION

In the Ultra Transcenders books

DBX-DEP

Each book explains CREATE FUNCTION in context, with comparison tables and the common traps.

Terms in this definition

• Event

  Table in Log Analytics where entries from Windows event logs are kept.

• FUNCTION

  Registered models count as functions in Unity Catalog, so this securable type governs them too: access is given through GRANT ... ON FUNCTION, and REST calls pass FUNCTION as securable_type.

• Serverless

  Compute tier for single Azure SQL databases that scales automatically, pauses when idle and charges by the second. It is offered in General Purpose and Hyperscale, not Business Critical, and reserved capacity does not apply.

• UDF

  Custom logic written in JavaScript and registered with a Cosmos DB container, callable only from queries. Calling one raises the request unit charge.

• Unity Catalog

  Azure Databricks' governance solution covering both data and AI in one place, with centralised permissions, auditing, data discovery and lineage.

• Governance

  Keeping cloud deployments in line with an organisation's rules on technology, security and compliance, helped by Azure Policy, tags and resource locks.

• LIKE

  Compares strings with a pattern that can contain the % and _ wildcards. Because it only understands character patterns, searching big volumes of text this way is much slower than using full-text search.

• Schema

  The middle part of a Unity Catalog name (catalog.schema.table), grouping tables, views, volumes, functions and models inside a catalog. A grant on it covers everything in it now and later, and nothing inside can be reached without USE SCHEMA.

Related terms

• Custom function

  Typically made by right-clicking a parameterised query and picking Create Function, this reusable Power Query function runs the same steps on each file or value. It keeps a link to the sample query it came from and is applied through Invoke Custom Function.

• DETERMINISTIC

  Tells the engine, in CREATE FUNCTION, that identical inputs always give identical outputs, which can help optimisation. The engine takes this on trust and does not verify it against the function's code.

• ENVIRONMENT clause

  Declares what a Python UDF needs, namely its environment_version and dependencies, when the function is created with CREATE FUNCTION.

• HANDLER

  Tells a Unity Catalog Python UDF which function in its body to start from, as part of CREATE FUNCTION. In a batch UDF, that function receives an iterator of pandas.Series.

• Invoke Custom Function

  Runs a custom function against every row of a table in Power Query, placing each result in a new column. To make such a function in the first place, use Create Function on a query built around a parameter.

• PARAMETER STYLE PANDAS

  Turns a Unity Catalog Python UDF into a batch function when used in CREATE FUNCTION. Its HANDLER receives an iterator of pandas.Series, and the output row count has to equal the input row count.

• RETURNS

  States what a function gives back, as a type or a table, inside CREATE FUNCTION. SQL functions can leave it out and have the type worked out from their body.

• Stored function

  Reusable KQL logic saved in the database schema as a user-defined function, using .create-or-alter function or .create function. A function declared with let, by contrast, is query-defined and only exists while that one query runs.