Build database objects with common language runtime (CLR) integration
Applies to: 
SQL Server
You can build database objects using the SQL Server integration with the .NET Framework common language runtime (CLR). Managed code that runs inside of SQL Server is called a CLR routine. These routines include:
- Scalar-valued user-defined functions (scalar UDFs)
- Table-valued user-defined functions (TVFs)
- User-defined procedures (UDPs)
- User-defined triggers
CLR routines have the same structure in managed code. They're mapped to public, static (shared in Visual Basic .NET) methods of a class. In addition to routines, user-defined types (UDTs) and user-defined aggregate functions can also be defined using the .NET Framework. UDTs and user-defined aggregates are mapped to entire .NET Framework classes.
Each type of .NET Framework routine has a Transact-SQL declaration and can be used anywhere in SQL Server that the Transact-SQL equivalent can be used. For instance, scalar UDFs can be used in any scalar expression. A TVF can be used in any FROM clause. A procedure can be invoked in an EXEC statement or invoked from a client application.
Execution of a CLR object (user-defined function, user-defined type, or trigger) on the common language runtime can take place on multiple threads (parallel plan), if the query optimizer decides it's beneficial. However, if a user-defined function accesses data, execution is on a serial plan.
The following table lists the articles covered in this section.
| Article | Description |
|---|---|
| Get started with CLR integration | Provides a brief overview of the libraries and namespaces required to compile object using CLR integration with SQL Server. Includes an example "Hello World" CLR stored procedure. |
| Supported .NET Framework libraries | Provides information on the .NET Framework libraries supported by CLR integration. |
| CLR integration programming model restrictions | Provides information about CLR integration programming model restrictions. |
| SQL Server data types in the .NET Framework | An overview of SQL Server data types and their .NET Framework equivalents. |
| CLR integration: custom attributes for CLR routines | Provides information about CLR integration custom attributes. |
| CLR user-defined functions | Describes how to implement and use the various types of CLR functions: table-valued, scalar, and user-defined aggregate functions. |
| CLR user-defined types | Describes how to implement and use CLR user-defined types. |
| CLR stored procedures | Describes how to implement and use CLR stored procedures. |
| CLR triggers | Describes how to implement and use CLR triggers. |