User-defined functions allow programmers to create their own routines and procedures that the computer can follow; they are the foundation of any programme and are also critical for modularity and code reuse because a programmer could create a user-defined function that performs a specific process and simply call it...
User Define Functions are functions that the programmer creates to execute a specific purpose. For example, if you want to get the sum of all array elements using your own function, you must define a function that takes array elements as an argument(s) and returns the sum of all elements.
User-defined functions in SQL Server are routines that accept parameters, perform an action, such as a complex computation, and return the result of that action as a value, similar to functions in programming languages. A single scalar value or a result set can be returned as the return value.
There are four categories of functions that can be roughly classified. Based on the element: one to one, many to one, onto function, one to one and onto function, into function.
The eight types are linear, power, quadratic, polynomial, rational, exponential, logarithmic, and sinusoidal.