Description

function-name
Names the user-defined function. The combination of name, schema name, the number of parameters, and the data type of each parameter (without regard for any length, precision, scale, or CCSID attributes of the data type) must not identify a user-defined function that exists at the current server.

For SQL naming, the function will be created in the schema specified by the implicit or explicit qualifier.

For system naming, the function will be created in the schema that is specified by the qualifier. If no qualifier is specified:

In general, more than one function can have the same name if the function signature of each function is unique.

Certain function names are reserved for system use. For more information see Choosing the Schema and Function Name.

(parameter-declaration,...)
Specifies the number of parameters of the function and the data type of each parameter. Although not required, you can give each parameter a name.

The maximum number of parameters allowed in CREATE FUNCTION (External Table) is 90. The maximum number of parameters may be additionally limited by the maximum number of parameters allowed by the licensed program that is used to compile the external program.

parameter-name
Names the parameter. Although not required, a parameter name can be specified for each parameter. The name cannot be the same as any other parameter-name in the parameter list.
data-type1
Specifies the data type of the input parameter. The data type can be a built-in data type or a distinct type.
built-in-type
Specifies a built-in data type. For a more complete description of each built-in data type, see CREATE TABLE. Some data types are not supported in all languages. For details on the mapping between the SQL data types and host language data types, see Embedded SQL Programming book. Built-in data type specifications can be specified if they correspond to the language that is used to write the user-defined function.
distinct-type-name
Specifies a user-defined distinct type. The length, precision, or scale attributes for the parameter are those of the source type of the distinct type (those specified on CREATE DISTINCT TYPE). For more information on creating a distinct type, see CREATE DISTINCT TYPE.

If the name of the distinct type is unqualified, the database manager resolves the schema name by searching the schemas in the SQL path.

Parameters with a large object (LOB) data type are not supported when PARAMETER STYLE JAVA is specified.

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.

AS LOCATOR
Specifies that the input parameter is a locator to the value rather than the actual value. You can specify AS LOCATOR only if the input parameter has a LOB data type or a distinct type based on a LOB data type. If AS LOCATOR is specified, FOR SBCS DATA or FOR MIXED DATA must not be specified.
RETURNS TABLE
Specifies the output table of the function.

Assume the number of parameters is N. For PARAMETER STYLE DB2GENERAL, there must be no more than (255-(N*2))/2 columns. For PARAMETER STYLE DB2SQL, there must be no more than (247-(N*2))/2 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, LONG VARGRAPHIC, or DataLink) or a distinct type (that is not based on a DataLink).

If a DATE or TIME is specified, the table function must return the date or time in ISO format.

If a CCSID is specified,

  • If AS LOCATOR is not specified, the result returned is assumed to be encoded in that CCSID.
  • If AS LOCATOR is specified and the CCSID of the data the locator points to is encoded in a different CCSID, the data is converted to the specified CCSID.

If a CCSID is not specified,

  • If AS LOCATOR is not specified, the result returned is assumed to be encoded in the CCSID of the job (or associated graphic CCSID of the job for graphic string return values).
  • If AS LOCATOR is specified, the data the locator points to is converted to the CCSID of the job, if the CCSID of the data the locator points to 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).
AS LOCATOR
Specifies that the function returns a locator to the value for the column rather than the actual value. You can specify AS LOCATOR only for a LOB data type or a distinct type based on a LOB data type. If AS LOCATOR is specified, FOR SBCS DATA or FOR MIXED DATA must not be specified.
LANGUAGE (language clause)
The language clause specifies the language of the external program.

If LANGUAGE is not specified, the LANGUAGE is determined from the program attribute information associated with the external program at the time the function is created. The language of the program is assumed to be C if:

C   
The external program is written in C.
C++
The external program is written in C++.
CL   
The external program is written in CL or ILE CL.
COBOL
The external program is written in COBOL.
COBOLLE
The external program is written in ILE COBOL.
FORTRAN
The external program is written in FORTRAN.
JAVA
The external program is written in JAVA. The database manager will call the user-defined function as a method in a Java(TM) class.
PLI
The external program is written in PL/I.
RPG
The external program is written in RPG.
RPGLE
The external program is written in ILE RPG.
PARAMETER STYLE
Specifies the conventions used for passing parameters to and returning the values from functions:
DB2GENERAL
This parameter style is used to specify the conventions for passing parameters to and returning the value from external functions that are defined as a method in a Java class. All applicable parameters are passed. The parameters are defined to be in the following order:
  • The first N parameters are the input parameters that are specified on the CREATE FUNCTION statement.
  • The next M parameters are the result columns of the function that are specified on the RETURNS TABLE clause.

DB2GENERAL is only allowed when the LANGUAGE is JAVA.

DB2SQL
All applicable parameters are passed. The parameters are defined to be in the following order:
  • The first N parameters are the input parameters that are specified on the CREATE FUNCTION statement.
  • The next M parameters are the result columns of the function that are specified on the RETURNS TABLE clause.
  • N parameters for indicator variables for the input parameters.
  • M parameters for the indicator variables of the result columns of the function that are specified on the RETURNS TABLE clause
  • A CHAR(5) output parameter for SQLSTATE. The SQLSTATE returned indicates the success or failure of the function. The SQLSTATE returned either be:
    • the SQLSTATE from the last SQL statement executed in the external program,
    • an SQLSTATE that is assigned by the external program.

      The user may set the SQLSTATE to any valid value in the external program to return an error or warning from the function.

  • A VARCHAR(517) input parameter for the fully qualified function name.
  • A VARCHAR(128) input parameter for the specific name.
  • A VARCHAR(70) output parameter for the message text.
  • A structure (consisting of an INTEGER followed by a CHAR(n)) input and output parameter for the scratchpad, if SCRATCH PAD was specified on the CREATE FUNCTION statement.
  • An INTEGER input parameter for the call type.
  • A structure for the dbinfo structure, if DBINFO was specified on the CREATE FUNCTION statement.
For more information about the parameters passed, see the include sqludf in the appropriate source file in library QSYSINC. For example, for C, sqludf can be found in QSYSINC/H.

Note that the language of the external function determines how the parameters are passed. For example, in C, any VARCHAR or CHAR parameters are passed as NUL-terminated strings. For more information, see the SQL Programming book. For Java routines, see the IBM(R) Developer Kit for Java.

SPECIFIC specific-name
Provides a unique name for the function. The name is implicitly or explicitly qualified with a schema name. The name, including the schema name, must not identify the specific name of another function or procedure that exists at the current server. If unqualified, the implicit qualifier is the same as the qualifier of the function name. If qualified, the qualifier must be the same as the qualifier of the function name.

If specific name is not specified, it is set to the function name. If a function or procedure with that specific name already exists, a unique name is generated similar to the rules used to generate unique table names.

DETERMINISTIC or NOT DETERMINISTIC
Specifies whether the function is deterministic.
NOT DETERMINISTIC
Specifies that the function will not always return the same result from successive function invocations with identical input arguments. NOT DETERMINISTIC should be specified if the function contains a reference to a special register, a non-deterministic function, or a sequence.
DETERMINISTIC
Specifies that the function will always return the same result from successive invocations with identical input arguments.
CONTAINS SQL, READS SQL DATA, MODIFIES SQL DATA, or NO SQL
Specifies whether the function can execute any SQL statements and, if so, what type. The database manager verifies that the SQL issued by the function is consistent with this specification. See Appendix B. Characteristics of SQL statements for a detailed list of the SQL statements that can be executed under each data access indication.
CONTAINS SQL
The function does not execute SQL statements that read or modify data.
NO SQL
The function does not execute SQL statements.
READS SQL DATA
The function does not execute SQL statements that modify data.
MODIFIES SQL DATA
The function can execute any SQL statement except those statements that are not supported in any function.
RETURNS NULL ON NULL INPUT or CALLED ON NULL INPUT
Specifies whether the function is called if any of the input arguments is null at execution time.
RETURNS NULL ON NULL INPUT
Specifies that the function is not invoked if any of the input arguments is null. The result is the null value.
CALLED ON NULL INPUT
Specifies that the function is to be invoked, if any, or all, argument values are null, making the function responsible for testing for null argument values. The function can return a null or nonnull value.
INHERIT SPECIAL REGISTERS
Specifies that existing values of special registers are inherited upon entry to the function.
STATIC DISPATCH
Specifies that the function is dispatched statically. All functions are statically dispatched.
DBINFO
Specifies whether or not the function requires the database information be passed.
DBINFO
Specifies that the database manager should pass a structure containing status information to the function. Table 50 contains a description of the DBINFO structure. Detailed information about the DBINFO structure can be found in sqludf in the appropriate source file in library QSYSINC. For example, for C, sqludf can be found in QSYSINC/H.
Table 50. DBINFO fields
Field Data Type Description
Relational database VARCHAR(128) The name of the current server.
Authorization ID VARCHAR(128) The run-time authorization ID.
CCSID Information
INTEGER
INTEGER
INTEGER
 
INTEGER
INTEGER
INTEGER
 
INTEGER
INTEGER
INTEGER
 
INTEGER
 
CHAR(8)
The CCSID information of the job. Three sets of three CCSIDs are returned. The following information identifies the three CCSIDs in each set:
  • SBCS CCSID
  • DBCS CCSID
  • Mixed CCSID
Following the three sets of CCSIDs is an integer that indicates which set of three sets of CCSIDs is applicable and eight bytes of reserved space.

If a CCSID is not explicitly specified for a parameter on the CREATE FUNCTION statement, the input string is assumed to be encoded in the CCSID of the job at the time the function is executed. If the CCSID of the input string is not the same as the CCSID of the parameter, the input string passed to the external function will be converted before calling the external program.

Target column VARCHAR(128)
VARCHAR(128)
VARCHAR(128)
If a user-defined function is specified on the right-hand side of a SET clause in an UPDATE statement, the following information identifies the target column:
  • Schema name
  • Base table name
  • Column name
If the user-defined function is not on the right-hand side of a SET clause in an UPDATE statement, these fields are blank.
Version and release CHAR(8) The version, release, and modification level of the database manager.
Platform INTEGER The server's platform type.
Number of table function column list entries SMALLINT The number of non-zero entries in the table function column list specified in the "Table function column list" field below.
Reserved CHAR(24) Reserved for future use.
Table function column list Pointer (16 Bytes) This field is a pointer to an array of short integers which is dynamically allocated by the database manager. Only the first n entries, where n is specified in the "Number of table function column list entries" field, are of interest, n may be equal to 0, and is less than or equal to the number of result columns defined for the function in the RETURNS TABLE clause. The values correspond to the ordinal numbers of the columns which this statement needs from the table function. A value of 1 means the first defined result column, 2 means the second defined result column, and so on. The values may be in any order. Note that n could be equal to zero for a statement that is similar to SELECT COUNT(*) FROM TABLE(TF(...)) AS QQ, where no actual column values are needed by the query.

This array represents an opportunity for optimization. The function need not return all values for all the result columns of the table function. Only a subset of the values may be needed in a particular context, and these are the columns identified (by number) in the array. Since this optimization may complicate the function logic, the function can choose to return every defined column.

NO DBINFO
Specifies that the function does not require the database information to be passed.
EXTERNAL ACTION or NO EXTERNAL ACTION
Specifies whether the function contains an external action.
EXTERNAL ACTION
The function performs some external action (outside the scope of the function program). Thus, the function must be invoked with each successive function invocation. EXTERNAL ACTION should be specified if the function contains a reference to another function that has an external action.
NO EXTERNAL ACTION
The function does not perform an external action. It need not be called with each successive function invocation.
FENCED or NOT FENCED
Specifies whether the external function runs in an environment that is isolated from the database manager environment.
FENCED
The function will run in a separate thread.

FENCED functions cannot keep SQL cursors open across individual calls to the function. However, the cursors in one thread are independent of the cursors in any other threads which reduces the possibility of cursor name conflicts.

NOT FENCED
The function may run in the same thread as the invoking SQL statement.

NOT FENCED functions can keep SQL cursors open across individual calls to the function. Since cursors can be kept open, the cursor position will also be preserved between calls to the function. However, cursor names may conflict since the UDF is now running in the same thread as the invoking SQL statement and other NOT FENCED UDFs.

NOT FENCED functions usually perform better than FENCED functions.

PROGRAM TYPE MAIN or PROGRAM TYPE MAIN
This parameter is allowed for compatibility with other products. It indicates whether the routine's external program is a program (*PGM) or a procedure in a service program (*SRVPGM).
PROGRAM TYPE MAIN
Specifies that the routine executes as the main entry point in a program. The external program must be a *PGM object.
PROGRAM TYPE SUB
Specifies that the procedure executes as a procedure in a service program. The external program must be a *SRVPGM object.
FINAL CALL
Specifies whether the function requires a final call (and a separate first call). For table functions, the call-type argument is ALWAYS present, regardless of which FINAL CALL option is chosen. The call-type argument indicates first call, open call, fetch call, close call, or final call.
FINAL CALL
Specifies that the function requires a final call (and a separate first call). It also controls when the scratchpad is re-initialized. If NO FINAL CALL is specified, then the database manager can only make three types of calls to the table function: open, fetch and close. However, if FINAL CALL is specified, then in addition to open, fetch and close, a first call and a final call can be made to the table function.Specifies that a final call is made to the function. To differentiate between final calls and other calls, the function receives an additional argument that specifies the type of call.

The types of calls are:

First Call
Specifies the first call to the function for this reference to the function in this SQL statement.
Open Call
Specifies a call to open the table function result in this SQL statement.
Fetch Call
Specifies a call to fetch a row from the table function in this SQL statement.
Close Call
Specifies a call to close the table function result in this SQL statement.
Final Call
Specifies the last call to the function to enable the function to free resources. If an error occurs, the database manager attempts to make the final call.

A final call occurs at these times:

  • End of statement: When the cursor is closed for cursor-oriented statements, or the execution of the statement has completed.
  • End of transaction: When normal end of statement processing does not occur. For example, the logic of an application, for some reason, bypasses closing the cursor.

If a commit operation occurs while a cursor defined as WITH HOLD is open, a final call is made when the cursor is closed or the application ends.

Commitable operations should not be performed during a FINAL CALL, because the FINAL CALL may occur during a close invoked as part of a COMMIT operation.

NO FINAL CALL
Specifies that the function does not require a final call (and a separate first call). However the open, fetch, and close calls are still made.
DISALLOW PARALLEL
Specifies that the function cannot be run in parallel. Table functions cannot run in parallel.
SCRATCHPAD
Specifies whether the function requires a static memory area.
SCRATCHPAD integer
Specifies that the function requires a persistent memory area of length integer. The integer can range from 1 to 16,000,000. If the memory area is not specified, the size of the area is 100 bytes. If parameter style DB2SQL is specified, a pointer is passed following the required parameters that points to a static storage area. Only 1 memory area will be allocated for the function.

The scope of a scratchpad is the SQL statement. For each reference to the function in an SQL statement, there is one scratchpad. For example, assuming that function UDFX was defined with the SCRATCHPAD keyword, two scratchpads are allocated for the two references to UDFX in the following SQL statement:

SELECT A.C1, B.C1 
  FROM TABLE(UDFX(:hv1)) AS A, TABLE(UDFX(:hv1)) AS B  
NO SCRATCHPAD
Specifies that the function does not require a persistent memory area.
EXTERNAL NAME external-program-name
Specifies the program, service program, or java class that will be executed when the function is invoked in an SQL statement. The name must identify a program, service program, or java class that exists at the application server at the time the function is invoked. If the naming option is *SYS and the name is not qualified:

The validity of the name is checked at the application server. If the format of the name is not correct, an error is returned.

If external-program-name is not specified, the external program name is assumed to be the same as the function name.

The program, service program, or java class need not exist at the time the function is created, but it must exist at the time the function is invoked.

A CONNECT, SET CONNECTION, RELEASE, DISCONNECT, COMMIT, ROLLBACK and SET TRANSACTION statement is not allowed in the external program of the function.

CARDINALITY bigint
Specifies an estimate of the expected number of rows to be returned by the function for the database manager to use during optimization. bigint must be in the range from 0 to 9 223 372 036 854 775 807 inclusive. The database manager assumes a finite value if CARDINALITY is not specified.

A table function that returns a row every time it is called and never returns the end-of-table condition has infinite cardinality. A query that invokes such a function and requires an eventual end-of-table condition before it can return any data will not return unless interrupted. Table functions that never return the end-of-table condition should not be used in queries involving DISTINCT, GROUP BY, or ORDER BY.