ALTER FUNCTION (Transact-SQL)
Alters an existing Transact-SQL or CLR function that was previously created by executing the CREATE FUNCTION statement, without changing permissions and without affecting any dependent functions, stored procedures, or triggers.
Scalar Functions
ALTER FUNCTION [ schema_name. ] function_name
( [ { @parameter_name [ AS ][ type_schema_name. ] parameter_data_type
[ = default ] }
[ ,...n ]
]
)
RETURNS return_data_type
[ WITH <function_option> [ ,...n ] ]
[ AS ]
BEGIN
function_body
RETURN scalar_expression
END
[ ; ]
Inline Table-valued Functions
ALTER FUNCTION [ schema_name. ] function_name
( [ { @parameter_name [ AS ] [ type_schema_name. ] parameter_data_type
[ = default ] }
[ ,...n ]
]
)
RETURNS TABLE
[ WITH <function_option> [ ,...n ] ]
[ AS ]
RETURN [ ( ] select_stmt [ ) ]
[ ; ]
Multistatement Table-valued Functions
ALTER FUNCTION [ schema_name. ] function_name
( [ { @parameter_name [ AS ] [ type_schema_name. ] parameter_data_type
[ = default ] }
[ ,...n ]
]
)
RETURNS @return_variable TABLE <table_type_definition>
[ WITH <function_option> [ ,...n ] ]
[ AS ]
BEGIN
function_body
RETURN
END
[ ; ]
CLR Functions
ALTER FUNCTION [ schema_name. ] function_name
( { @parameter_name [AS] [ type_schema_name. ] parameter_data_type
[ = default ] }
[ ,...n ]
)
RETURNS { return_data_type | TABLE <clr_table_type_definition> }
[ WITH <clr_function_option> [ ,...n ] ]
[ AS ] EXTERNAL NAME <method_specifier>
[ ; ]
<method_specifier>::=
assembly_name.class_name.method_name
Function Options
<function_option>::=
{
[ ENCRYPTION ]
| [ SCHEMABINDING ]
| [ RETURNS NULL ON NULL INPUT | CALLED ON NULL INPUT ]
| [ EXECUTE_AS_Clause ]
}
<clr_function_option>::=
}
[ RETURNS NULL ON NULL INPUT | CALLED ON NULL INPUT ]
| [ EXECUTE_AS_Clause ]
}
Table Type Definitions
<table_type_definition>:: =
( { <column_definition> <column_constraint>
| <computed_column_definition> }
[ <table_constraint> ] [ ,...n ]
)
<clr_table_type_definition>:: =
( { column_name data_type } [ ,...n ] )
<column_definition>::=
{
{ column_name data_type }
[ [ DEFAULT constant_expression ]
[ COLLATE collation_name ] | [ ROWGUIDCOL ]
]
| [ IDENTITY [ (seed , increment ) ] ]
[ <column_constraint> [ ...n ] ]
}
<column_constraint>::=
{
[ NULL | NOT NULL ]
{ PRIMARY KEY | UNIQUE }
[ CLUSTERED | NONCLUSTERED ]
[ WITH FILLFACTOR = fillfactor
| WITH ( < index_option > [ , ...n ] )
[ ON { filegroup | "default" } ]
| [ CHECK ( logical_expression ) ] [ ,...n ]
}
<computed_column_definition>::=
column_name AS computed_column_expression
<table_constraint>::=
{
{ PRIMARY KEY | UNIQUE }
[ CLUSTERED | NONCLUSTERED ]
( column_name [ ASC | DESC ] [ ,...n ] )
[ WITH FILLFACTOR = fillfactor
| WITH ( <index_option> [ , ...n ] )
| [ CHECK ( logical_expression ) ] [ ,...n ]
}
<index_option>::=
{
PAD_INDEX = { ON | OFF }
| FILLFACTOR = fillfactor
| IGNORE_DUP_KEY = { ON | OFF }
| STATISTICS_NORECOMPUTE = { ON | OFF }
| ALLOW_ROW_LOCKS = { ON | OFF }
| ALLOW_PAGE_LOCKS ={ ON | OFF }
}
- schema_name
Is the name of the schema to which the user-defined function belongs.
- function_name
Is the user-defined function to be changed.
NoteParentheses are required after the function name even if a parameter is not specified.
- @parameter_name
Is a parameter in the user-defined function. One or more parameters can be declared.
A function can have a maximum of 2,100 parameters. The value of each declared parameter must be supplied by the user when the function is executed, unless a default for the parameter is defined.
Specify a parameter name by using an at sign (@) as the first character. The parameter name must comply with the rules for identifiers. Parameters are local to the function; the same parameter names can be used in other functions. Parameters can take the place only of constants; they cannot be used instead of table names, column names, or the names of other database objects.
NoteANSI_WARNINGS is not honored when passing parameters in a stored procedure, user-defined function, or when declaring and setting variables in a batch statement. For example, if a variable is defined as char(3), and then set to a value larger than three characters, the data is truncated to the defined size and the INSERT or UPDATE statement succeeds.
- [ type_schema_name. ] parameter_data_type
Is the parameter data type and optionally, the schema to which it belongs. For Transact-SQL functions, all data types, including CLR user-defined types, are allowed except the timestamp data type. For CLR functions, all data types, including CLR user-defined types, are allowed except text, ntext, image, and timestamp data types. The nonscalar types cursor and table cannot be specified as a parameter data type in either Transact-SQL or CLR functions.
If type_schema_name is not specified, the SQL Server 2005 Database Engine looks for the parameter_data_type in the following order:
The schema that contains the names of SQL Server system data types.
The default schema of the current user in the current database.
The dbo schema in the current database.
- [ =default ]
Is a default value for the parameter. If a default value is defined, the function can be executed without specifying a value for that parameter.
NoteDefault parameter values can be specified for CLR functions except for varchar(max) and varbinary(max) data types.
When a parameter of the function has a default value, the keyword DEFAULT must be specified when calling the function to retrieve the default value. This behavior is different from using parameters with default values in stored procedures in which omitting the parameter also implies the default value.
- return_data_type
Is the return value of a scalar user-defined function. For Transact-SQL functions, all data types, including CLR user-defined types, are allowed except the timestamp data type. For CLR functions, all data types, including CLR user-defined types, are allowed except text, ntext, image, and timestamp data types. The nonscalar types cursor and table cannot be specified as a return data type in either Transact-SQL or CLR functions.
- function_body
Specifies that a series of Transact-SQL statements, which together do not produce a side effect such as modifying a table, define the value of the function. function_body is used only in scalar functions and multistatement table-valued functions.
In scalar functions, function_body is a series of Transact-SQL statements that together evaluate to a scalar value.
In multistatement table-valued functions, function_body is a series of Transact-SQL statements that populate a TABLE return variable.
- scalar_expression
Specifies that the scalar function returns a scalar value.
- TABLE
Specifies that the return value of the table-valued function is a table. Only constants and @local_variables can be passed to table-valued functions.
In inline table-valued functions, the TABLE return value is defined through a single SELECT statement. Inline functions do not have associated return variables.
In multistatement table-valued functions, @return_variable is a TABLE variable used to store and accumulate the rows that should be returned as the value of the function. @return_variable can be specified only for Transact-SQL functions and not for CLR functions.
- select-stmt
Is the single SELECT statement that defines the return value of an inline table-valued function.
- EXTERNAL NAME <method_specifier>assembly_name.class_name.method_name
Specifies the method of an assembly to bind with the function. assembly_name must match an existing assembly in SQL Server in the current database with visibility on. class_name must be a valid SQL Server identifier and must exist as a class in the assembly. If the class has a namespace-qualified name that uses a period (.) to separate namespace parts, the class name must be delimited by using brackets ([ ]) or quotation marks (" "). method_name must be a valid SQL Server identifier and must exist as a static method in the specified class.
NoteBy default, SQL Server cannot execute CLR code. You can create, modify, and drop database objects that reference common language runtime modules; however, you cannot execute these references in SQL Server until you enable the clr enabled option. To enable the option, use sp_configure.
- <table_type_definition>( { <column_definition> <column_constraint> | <computed_column_definition> } [ <table_constraint> ] [ ,...n ])
Defines the table data type for a Transact-SQL function. The table declaration includes column definitions and column or table constraints.
- < clr_table_type_definition > ( { column_namedata_type } [ ,...n ] )
Defines the table data types for a CLR function. The table declaration includes only column names and data types.
<function_option>::= and <clr_function_option>::=
Specifies the function will have one or more of the following options.
- ENCRYPTION
Indicates that the Database Engine encrypts the catalog view columns that contains the text of the ALTER FUNCTION statement. Using ENCRYPTION prevents the function from being published as part of SQL Server replication. ENCRYPTION cannot be specified for CLR functions.
- SCHEMABINDING
Specifies that the function is bound to the database objects that it references. This condition will prevent changes to the function if other schema bound objects are referencing it.
The binding of the function to the objects it references is removed only when one of the following actions occurs:
The function is dropped.
The function is modified by using the ALTER statement with the SCHEMABINDING option not specified.
For a list of conditions that must be met before a function can be schema bound, see CREATE FUNCTION (Transact-SQL).
- RETURNS NULL ON NULL INPUT | CALLED ON NULL INPUT
Specifies the OnNULLCall attribute of a scalar-valued function. If not specified, CALLED ON NULL INPUT is implied by default. This means that the function body executes even if NULL is passed as an argument.
If RETURNS NULL ON NULL INPUT is specified in a CLR function, it indicates that SQL Server can return NULL when any of the arguments it receives is NULL, without actually invoking the body of the function. If the method specified in <method_specifier> already has a custom attribute that indicates RETURNS NULL ON NULL INPUT, but the ALTER FUNCTION statement indicates CALLED ON NULL INPUT, the ALTER FUNCTION statement takes precedence. The OnNULLCall attribute cannot be specified for CLR table-valued functions.
- EXECUTE AS Clause
Specifies the security context under which the user-defined function is executed. Therefore, you can control which user account SQL Server uses to validate permissions on any database objects referenced by the function.
NoteEXECUTE AS cannot be specified for inline user-defined functions.
For more information, see EXECUTE AS Clause (Transact-SQL).
< column_definition >::=
Defines the table data type. The table declaration includes column definitions and constraints. For CLR functions, only column_name and data_type can be specified.
< column_constraint >::= and < table_constraint>::=
Defines the constraint for a specified column or table. For CLR functions, the only constraint type allowed is NULL. Named constraints are not allowed.
<computed_column_definition>::=
Specifies a computed column. For more information about computed columns, see CREATE TABLE (Transact-SQL).
<index_option>::=
Specifies the index options for the PRIMARY KEY or UNIQUE index. For more information about index options, see CREATE INDEX (Transact-SQL).
ALTER FUNCTION cannot be used to change a scalar-valued function to a table-valued function, or vice versa. Also, ALTER FUNCTION cannot be used to change an inline function to a multistatement function, or vice versa. ALTER FUNCTION cannot be used to change a Transact-SQL function to a CLR function or vice-versa.
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
MOVE CONVERSATION
RECEIVE
SEND
