ALTER FUNCTION (SQL Table)
The ALTER FUNCTION (SQL Table) statement alters an SQL table function at the current server.
Invocation
This statement can be embedded in an application program or issued interactively. It is an executable statement that can be dynamically prepared.
Authorization
The privileges held by the authorization ID of the statement must include at least one of the following:
- For the function identified in the statement:
- The ALTER privilege for the function, and
- The system authority *EXECUTE on the library containing the function.
- Administrative authority
If a different external program is specified, the privileges held by the authorization ID of the statement must also include the same privileges required to create a new external table function. For more information, see CREATE FUNCTION (SQL Table).
For information about the system authorities corresponding to SQL privileges, see Corresponding System Authorities When Checking Privileges to a Function or Procedure, Corresponding System Authorities When Checking Privileges to a Table or View, and Corresponding System Authorities When Checking Privileges to a Distinct Type.
Syntax
>>-ALTER--------------------------------------------------------> >--+-FUNCTION--function-name--+------------------------------+-+--> | '-(--+--------------------+--)-' | | | .-,--------------. | | | | V | | | | '---parameter-type-+-' | '-SPECIFIC FUNCTION--specific-name--------------------------' .-ALTER-. >--+-+-------+--+----------+--option-list---------+------------>< | '-RESTRICT-' | '-REPLACE--+----------+--routine-specification-' '-RESTRICT-' parameter-type |----data-type1--+------------+---------------------------------| '-AS LOCATOR-' data-type1, data-type2, data-type3 |--+-built-in-type------+---------------------------------------| '-distinct-type-name-' routine-specification |----(--+---------------------------+--)------------------------> | .-,---------------------. | | V | | '---parameter-declaration-+-' .-,-----------------------. V | >--RETURNS TABLE--(----column-name--data-type2-+--)-------------> >--+-------------+----------------------------------------------> '-option-list-' >--+----------------------+--SQL-routine-body-------------------| '-SET OPTION-statement-' parameter-declaration |--parameter-name--data-type3-----------------------------------|
- The clauses in the option-list can be specified in any order.
Description
- FUNCTION or SPECIFIC FUNCTION
- Identifies
the function to alter. function-name must identify an SQL table
function that exists at the current server.
The specified function is altered. The owner of the function and all privileges on the function are preserved.
- FUNCTION function-name
- Identifies the function by its name. The function-name must identify exactly one function. The function may have any number of parameters defined for it. If there is more than one function of the specified name in the specified or implicit schema, an error is returned.
- FUNCTION function-name (parameter-type,...)
- Identifies the function by its function signature, which uniquely
identifies the function. The function-name (parameter-type,...) must
identify a function with the specified function signature. The specified
parameters must match the data types in the corresponding position
that were specified when the function was created. The number of data
types, and the logical concatenation of the data types is used to
identify the specific function instance which is being altered. Synonyms
for data types are considered a match.
If function-name() is specified, the function identified must have zero parameters.
- function-name
- Identifies the name of the function.
- (parameter-type,...)
- Identifies the parameters of the function.
If an unqualified distinct type name is specified, the database manager searches the SQL path to resolve the schema name for the distinct type.
For data types that have a length, precision, or scale attribute, use one of the following:
- Empty parenthesis indicates that the database manager ignores the attribute when determining whether the data types match. For example, DEC() will be considered a match for a parameter of a function defined with a data type of DEC(7,2). However, FLOAT cannot be specified with empty parenthesis because its precision value indicates a specific data type (REAL or DOUBLE).
- If a specific value for a length, precision, or scale attribute is specified, the value must exactly match the value that was specified (implicitly or explicitly) in the CREATE FUNCTION statement. If the data type is FLOAT, the precision does not have to exactly match the value that was specified because matching is based on the data type (REAL or DOUBLE).
- If length, precision, or scale is not explicitly specified, and empty parentheses are not specified, the default attributes of the data type are implied. The implicit length must exactly match the value that was specified (implicitly or explicitly) in the CREATE FUNCTION statement.
Specifying the FOR DATA clause or CCSID clause is optional. Omission of either clause indicates that the database manager ignores the attribute when determining whether the data types match. If either clause is specified, it must match the value that was implicitly or explicitly specified in the CREATE FUNCTION statement.
- AS LOCATOR
Specifies that the function is defined to receive a
locator for this parameter. If AS LOCATOR is specified, the data type
must be a LOB or XML or a distinct type based on a LOB or XML.
- SPECIFIC FUNCTION specific-name
- Identifies the function by its specific name. The specific-name must identify a specific function that exists at the current server.
- ALTER option-list
- Indicates that one or more of the options of the function are to be altered. If ALTER FUNCTION ALTER option-list is specified and an option is not specified, the value from the existing function definition is used. See CREATE FUNCTION (SQL Table) for a description of each option.
- REPLACE routine-specification
- Indicates
that the existing function definition, including options and parameters,
is to be replaced by those specified in this statement. The values
of all options are replaced when a function is replaced. If an option
is not specified, the same default is used as when a new SQL table
function is created, for more information see CREATE FUNCTION (SQL Table).If the routine has a comment or label, they are removed
from the routine definition.
- RESTRICT
- Indicates that the function will not be altered or replaced if it is referenced by any function, materialized query table, procedure, trigger, or view.
- (parameter-declaration,…)
- Specifies the number of parameters of the function, the data type
of each parameter, and the name of each parameter.
The maximum number of parameters allowed in an SQL function is
1024.- parameter-name
- Names the parameter. The name is used to refer to the parameter within the body of the function. The name cannot be the same as any other parameter-name in the parameter list.
- data-type3
- Specifies the data type of the input parameter. If a CCSID is specified, the parameter will be converted to that CCSID prior to passing it to the function. If a CCSID is not specified, the CCSID is determined by the default CCSID at the current server at the time the function is invoked.
- RETURNS TABLE
- Specifies
the output table of the function.
Assume the number of parameters is N. There must be no more than
1025 - N columns.- column-name
- Specifies the name of a column of the output table. Do not specify the same name more than once.
- data-type2
- Specifies the data type and attributes of the output.
You can specify any built-in data type (except LONG VARCHAR, or LONG VARGRAPHIC) or a distinct type.
If a CCSID is specified and the CCSID of the return data is encoded in a different CCSID, the data is converted to the specified CCSID.
If a CCSID is not specified the return data is converted to the CCSID of the job (or associated graphic CCSID of the job for graphic string return values), if the CCSID of the return data is encoded in a different CCSID. To avoid any potential loss of characters during the conversion, consider explicitly specifying a CCSID that can represent any characters that will be returned from the function. This is especially important if the data type is graphic string data. In this case, consider using CCSID 1200 or 13488 (Unicode graphic string data).
- option-list
- List of options for the function being altered. These options are the same ones that are listed above under ALTER option-list. If a specific option is not specified, the same default that is used when a new function is created is used. For more information see CREATE FUNCTION (SQL Table).
- SET OPTION-statement
- Specifies the options that will be used to create the function.
For example, to create a debuggable function, the following statement
could be included:
For more information, see SET OPTION.SET OPTION DBGVIEW = *SOURCEThe options CNULRQD, COMPILEOPT, NAMING, and SQLCA are not allowed in the ALTER FUNCTION statement.
- SQL-routine-body
- Specifies a single SQL statement, including a compound statement.
See SQL control statements for more information
about defining SQL functions.
A call to a procedure that issues a CONNECT, SET CONNECTION, RELEASE, DISCONNECT, COMMIT, ROLLBACK, and SET TRANSACTION statement is not allowed in a function.
The SQL-routine-body must contain at least one RETURN statement and a RETURN statement must be executed when the function is called.
ALTER PROCEDURE (SQL), ALTER FUNCTION (SQL Scalar), and ALTER FUNCTION (SQL Table) with a REPLACE keyword are not allowed in an SQL-routine-body.
Notes
General considerations for defining or replacing functions: See CREATE FUNCTION (SQL Table) for general information about defining a function. ALTER FUNCTION (SQL Table) allows individual attributes to be altered while preserving the privileges on the function.
Cascaded effects: If REPLACE is specified
without RESTRICT and the function signature or result data types are
altered, the results from any function, materialized query table,
procedure, trigger, or view that references the function may be unpredictable.
Any referenced objects should be recreated.
Syntax alternatives: The following keywords are synonyms supported for compatibility to prior releases. These keywords are non-standard and should not be used:
- The keywords VARIANT and NOT VARIANT can be used as synonyms for NOT DETERMINISTIC and DETERMINISTIC.
- The keywords NULL CALL and NOT NULL CALL can be used as synonyms for CALLED ON NULL INPUT and RETURNS NULL ON NULL INPUT.
- The keywords IS DETERMINISTIC may be used as a synonym for DETERMINISTIC.
Example
Modify the definition for an SQL table function to set the estimated cardinality to 10,000.
ALTER FUNCTION GET_TABLE
ALTER CARDINALITY 10000