Search results
May 20, 2011 · SET @i = @i + 1. /* do some work */. Be it noted that if you intend to use the index in the loop you may want to increment last thing instead of first, depending on your use case. Also note that default value for local variable is not supported in plain SQL. Hence you need separate SET @i = 0 before for loop.
AS: Begins the body of the function. BEGIN and END: Enclose the set of SQL statements that make up the function’s logic. The statements are executed when the function is called. RETURN expression: This statement specifies the value that the function will return. The data type of the returned value should match the return_datatype specified ...
- Overview
- Arguments
- Best Practices
- Data Types
- General Remarks
- Interoperability
- Limitations and Restrictions
- Permissions
- Examples
- See Also
Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance
Creates a user-defined function. A user-defined function is a Transact-SQL or common language runtime (CLR) routine that accepts parameters, performs an action, such as a complex calculation, and returns the result of that action as a value. The return value can either be a scalar (single) value or a table. Use this statement to create a reusable routine that can be used in these ways:
•In Transact-SQL statements such as SELECT
•In applications calling the function
•In the definition of another user-defined function
•To parameterize a view or improve the functionality of an indexed view
OR ALTER
Applies to: SQL Server (Starting with SQL Server 2016 (13.x) SP1) and Azure SQL Database
Conditionally alters the function only if it already exists.
schema_name
Is the name of the schema to which the user-defined function belongs.
function_name
If a user-defined function is not created with the SCHEMABINDING clause, changes that are made to underlying objects can affect the definition of the function and produce unexpected results when it is invoked. We recommend that you implement one of the following methods to ensure that the function does not become outdated because of changes to its underlying objects:
•Specify the WITH SCHEMABINDING clause when you are creating the function. This ensures that the objects referenced in the function definition cannot be modified unless the function is also modified.
•Execute the sp_refreshsqlmodule stored procedure after modifying any object that is specified in the definition of the function.
Important
If parameters are specified in a CLR function, they should be SQL Server types as defined previously for scalar_parameter_data_type. For information about comparing SQL Server system data types to CLR integration data types or .NET Framework common language runtime data types, see Mapping CLR Parameter Data.
For SQL Server to reference the correct method when it is overloaded in a class, the method indicated in must have the following characteristics:
•Receive the same number of parameters as specified in [ ,...n ].
•Receive all the parameters by value, not by reference.
•Use parameter types that are compatible with those specified in the SQL Server function.
If the return data type of the CLR function specifies a table type (RETURNS TABLE), the return data type of the method in should be of type IEnumerator or IEnumerable, and it is assumed that the interface is implemented by the creator of the function. Unlike Transact-SQL functions, CLR functions cannot include PRIMARY KEY, UNIQUE, or CHECK constraints in . The data types of columns specified in must match the types of the corresponding columns of the result set returned by the method in at execution time. This type-checking is not performed at the time the function is created.
Scalar functions can be invoked where scalar expressions are used. This includes computed columns and CHECK constraint definitions. Scalar functions can also be executed by using the EXECUTE statement. Scalar functions must be invoked by using at least the two-part name of the function ( . ). For more information about multipart nam...
The following statements are valid in a function:
•Assignment statements.
•Control-of-Flow statements except TRY...CATCH statements.
•DECLARE statements defining local data variables and local cursors.
•SELECT statements that contain select lists with expressions that assign values to local variables.
•Cursor operations referencing local cursors that are declared, opened, closed, and deallocated in the function. Only FETCH statements that assign values to local variables using the INTO clause are allowed; FETCH statements that return data to the client are not allowed.
User-defined functions cannot be used to perform actions that modify the database state.
User-defined functions cannot contain an OUTPUT INTO clause that has a table as its target.
The following Service Broker statements cannot be included in the definition of a Transact-SQL user-defined function:
•BEGIN DIALOG CONVERSATION
•END CONVERSATION
•GET CONVERSATION GROUP
Requires CREATE FUNCTION permission in the database and ALTER permission on the schema in which the function is being created. If the function specifies a user-defined type, requires EXECUTE permission on the type.
A. Using a scalar-valued user-defined function that calculates the ISO week
The following example creates the user-defined function ISOweek. This function takes a date argument and calculates the ISO week number. For this function to calculate correctly, SET DATEFIRST 1 must be invoked before the function is called. The example also shows using the EXECUTE AS clause to specify the security context in which a stored procedure can be executed. In the example, the option CALLER specifies that the procedure will be executed in the context of the user that calls it. The other options that you can specify are SELF, OWNER, and user_name. Here is the function call. Notice that DATEFIRST is set to 1. Here is the result set.
B. Creating an inline table-valued function
The following example returns an inline table-valued function in the AdventureWorks2022 database. It returns three columns ProductID, Name and the aggregate of year-to-date totals by store as YTD Total for each product sold to the store. To invoke the function, run this query.
C. Creating a multi-statement table-valued function
The following example creates the table-valued function fn_FindReports(InEmpID) in the AdventureWorks2022 database. When supplied with a valid employee ID, the function returns a table that corresponds to all the employees that report to the employee either directly or indirectly. The function uses a recursive common table expression (CTE) to produce the hierarchical list of employees. For more information about recursive CTEs, see WITH common_table_expression (Transact-SQL).
Feb 25, 2020 · ALTER is very similar to CREATE and it simply modifies the existing function. To delete a function, we’ll use statement DROP FUNCTION and the name of that function. Note: If we would work with procedures, we would use CREATE PROCEDURE, ALTER PROCEDURE, and DROP PROCEDURE. A Simple User-Defined Function
Aug 25, 2021 · Aggregate functions. COUNT (expr) − the count of values for the rows within the group. SUM (expr) − the sum of values within the group. AVG (expr) − the average value for the rows within the group. MIN (expr) − the minimum value within the group. MAX (expr) − the maximum value within the group.
To create a function in SQL Server with T-SQL uses the following syntax: CREATE OR ALTER FUNCTION function_name(parameters) SQL_statements. RETURN return_value. The function_name is the name of the function in the above syntax. The input parameters are given in the round brackets. It also has the data types.
People also ask
What is function in SQL Server?
What is a return statement in SQL?
Are functions a good idea in SQL Server?
How do I use a function in SQL Server?
SQL User-defined functions. SQL User-Defined Functions (UDFs) are custom functions created by users to perform specific tasks within a relational database management system (RDBMS). These functions encapsulate a set of SQL statements, allowing users to execute complex operations, calculations, or data manipulations with a single function call.
