Using the CLR Function Once deployed to the SQL Server, the CLR function appears in the Programmability, Functions, Scalar-valued Functions folder of the database, much like a T-SQL user-defined ...

What Is Tsql Function? Users-defined functions are Transact-SQL or CLRS (common language runtime) routines that take parameters, perform actions, such as complex calculations, and return the results ...

When you use a scalar function in the SELECT list of a query, the function gets called for every single row in the result set. This can reduce the performance of large queries by a significant amount.

As I recall, the scalar function inlining query optimization improvement, made it to GA in SQL Server 2019 before it made it to Azure SQL DB.