SQL Server User Defined Functions - Examples Tutorial

Types of User Defined Functions in SQL Server

SQL Server supports three main types of UDFs: scalar functions, inline table-valued functions, and multi-statement table-valued functions.

Each type serves different purposes depending on the complexity and expected output.

• Scalar Functions: Return a single value of any SQL data type.
• Inline Table-Valued Functions: Return a table result defined by a single SELECT statement.
• Multi-Statement Table-Valued Functions: Return a table and allow multiple statements to populate it.

Scalar Function Example

Scalar functions return a single value and are useful for computations or formatting.

Here is an example that calculates the sales tax for a given amount.

Inline Table-Valued Function Example

Inline table-valued functions return a table and are defined by a single SELECT statement.

They are efficient and can be used like views with parameters.

Multi-Statement Table-Valued Function Example

Multi-statement table-valued functions allow multiple statements to build the returned table.

They are useful for complex logic but can have performance overhead.