This section will be dedicated to the use of functions. We will see what the most important built-in functions of SQL Server are and how to use them, as well as declare, execute and manipulate our own user functions: both scalar functions and table functions
A function can be defined as a set of instructions that performs a certain task automatically. Built-in functions are those system-specific functions, already defined by SQL-Server
Built-in scalar functions
Scalar functions operate on one value and return another. There are different types of scalar functions.
A function can be defined as a set of instructions that performs a certain task automatically. User-defined functions are those for defining your own custom functionality
Scalar functions return a single scalar value whose data type will be defined in the RETURN clause
Table functions return a result set in the form of a table. We will review the statements to create, execute, modify and eliminate user functions with examples