The key differences between SQL Server stored procedures and functions, based on the Microsoft and Azure websites:
| Feature | Stored Procedure | Function |
|---|---|---|
| Return value | Can return zero or more values | Must return a single value |
| Parameters | Can have input, output, or both input and output parameters | Can only have input parameters |
| Transactions | Can be used in transactions | Cannot be used in transactions |
| Security | Can be secured with permissions | Cannot be secured with permissions |
| Performance | Can be compiled and cached, which can improve performance | Is not compiled and cached, so performance is not as good |
| Usage | Used to perform complex operations or to group multiple SQL statements | Used to perform a specific task and return a value |
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Here are some additional details about each of these differences:
- Return value: A stored procedure can return zero or more values, while a function must return a single value. This is because functions are designed to be used in expressions, while stored procedures are designed to be called as a unit.
- Parameters: A stored procedure can have input, output, or both input and output parameters. Input parameters are used to pass values to the stored procedure, output parameters are used to return values from the stored procedure, and both input and output parameters can be used to pass values to and from the stored procedure. Functions can only have input parameters.
- Transactions: A stored procedure can be used in transactions, which means that multiple SQL statements can be executed as a single unit. This can help to ensure data integrity. Functions cannot be used in transactions.
- Security: Stored procedures can be secured with permissions, which means that only authorized users can execute them. Functions cannot be secured with permissions.
- Performance: Stored procedures can be compiled and cached, which can improve performance. This is because the compiled code is stored in memory and can be executed more quickly than the uncompiled code. Functions are not compiled and cached, so performance is not as good.
- Usage: Stored procedures are used to perform complex operations or to group multiple SQL statements. Functions are used to perform a specific task and return a value.
In general, stored procedures are more versatile than functions. They can be used to perform a wider range of tasks, and they can be used to improve performance. However, functions are simpler to write and understand, and they are often used to perform simple tasks.
The best choice for a particular task will depend on the specific requirements of the application.
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