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SQL Anywhere 10.0.1 » SQL Anywhere Server - SQL Reference » SQL Statements

CREATE EXTERNLOGIN statement Next Page

CREATE FUNCTION statement


Use this statement to create a new function in the database.

Syntax 1

CREATE [ TEMPORARY ] FUNCTION [ owner.]function-name ( [ parameter, ... ] )
RETURNS data-type routine-characteristics
{ compound-statement
| AS tsql-compound-statement
| external-name }

Syntax 2

CREATE FUNCTION [ owner.]function-name ( [ parameter, ... ] )
RETURNS data-type
URL url-string
[ HEADER header-string ]
[ SOAPHEADER soap-header-string ]
[ TYPE { 'HTTP[:{ GET | POST } ] ' | 'SOAP[:{ RPC | DOC } ]' } ]
[ NAMESPACE namespace-string ]
[ CERTIFICATE certificate-string ]
[ CLIENTPORT clientport-string ]
[ PROXY proxy-string ]

url-string :
'{ HTTP
| HTTPS
|HTTPS_FIPS}://[user:password@]hostname[:port] }[/path]'

parameter :
IN parameter-name data-type [ DEFAULT expression ]

routine-characteristics
ON EXCEPTION RESUME | [ NOT ] DETERMINISTIC

tsql-compound-statement:
sql-statement
sql-statement
...

external-name:
EXTERNAL NAME library-call
| EXTERNAL NAME java-call LANGUAGE JAVA

library-call :
[operating-system:]function-name@library; ...

operating-system :
NetWare | Unix

java-call :
[package-name.]class-name.method-name method-signature

method-signature :
([field-descriptor, ... ]) return-descriptor

field-descriptor | return-descriptor :
Z | B | S | I | J | F | D | C | V | [descriptor | Lclass-name;

Parameters

CREATE FUNCTION clause    Parameter names must conform to the rules for database identifiers. They must have a valid SQL data type, and must be prefixed by the keyword IN, signifying that the argument is an expression that provides a value to the function.

When functions are executed, not all parameters need to be specified. If a default value is provided in the CREATE FUNCTION statement, missing parameters are assigned the default values. If an argument is not provided by the caller and no default is set, an error is given.

Specifying TEMPORARY (CREATE TEMPORARY FUNCTION) means that the function is visible only by the connection that created it, and that it is automatically dropped when the connection is dropped. Temporary functions can also be explicitly dropped. You cannot perform ALTER, GRANT, or REVOKE on them, and, unlike other functions, temporary functions are not recorded in the catalog or transaction log.

Temporary functions execute with the permissions of their creator (current user), and can only be owned by their creator. Therefore, do not specify owner when creating a temporary function.

Temporary functions can be created and dropped when connected to a read-only database.

compound-statement    A set of SQL statements bracketed by BEGIN and END, and separated by semicolons. See BEGIN statement

tsql-compound-statement    A batch of Transact-SQL statements. See Transact-SQL batch overview, and CREATE PROCEDURE statement [T-SQL].

EXTERNAL NAME clause    A function using the EXTERNAL NAME clause is a wrapper around a call to a function in an external library. A function using EXTERNAL NAME can have no other clauses following the RETURNS clause. The library name may include the file extension, which is typically .dll on Windows, .so on Unix, and .nlm on NetWare. In the absence of the extension, the software appends the platform-specific default file extension for libraries. On NetWare, if no NLM name is given, the NLM containing the symbol must already be loaded when the function is called.

For information about external library calls, see Calling external libraries from procedures.

EXTERNAL NAME LANGUAGE JAVA clause    A function that uses EXTERNAL NAME with a LANGUAGE JAVA clause is a wrapper around a Java method.

For information on calling Java procedures, see CREATE PROCEDURE statement.

ON EXCEPTION RESUME clause    Use Transact-SQL -like error handling. See CREATE PROCEDURE statement.

NOT DETERMINISTIC clause    A function specified as NOT DETERMINISTIC is re-evaluated each time it is called in a query. The results of functions not specified in this manner may be cached for better performance, and re-used each time the function is called with the same parameters during query evaluation.

Functions that have side effects such as modifying the underlying data should be declared as NOT DETERMINISTIC. For example, a function that generates primary key values and is used in an INSERT ... SELECT statement should be declared NOT DETERMINISTIC:

CREATE FUNCTION keygen( increment INTEGER )
RETURNS INTEGER
NOT DETERMINISTIC
BEGIN
  DECLARE keyval INTEGER;
  UPDATE counter SET x = x + increment;
  SELECT counter.x INTO keyval FROM counter;
  RETURN keyval
END
INSERT INTO new_table
SELECT keygen(1), ...
FROM old_table;

Functions may be declared as DETERMINISTIC if they always return the same value for given input parameters. Future versions of the software may use this declaration to allow optimizations that are unsafe for functions that could return different values for the same input.

URL clause    For use only when defining an HTTP or SOAP web services client function. Specifies the URL of the web service. The optional user name and password parameters provide a means of supplying the credentials needed for HTTP basic authentication. HTTP basic authentication base-64 encodes the user and password information and passes it in the "Authentication" header of the HTTP request.

Specifying HTTPS_FIPS forces the system to use the FIPS libraries. If HTTPS_FIPS is specified, but no FIPS libraries are present, non-FIPS libraries are used instead.

HEADER clause    When creating HTTP web service client functions, use this clause to add or modify HTTP request header entries. Only printable ASCII characters can be specified for HTTP headers, and they are case-insensitive. For more information about how to use this clause, see the HEADER clause of the CREATE PROCEDURE statement.

For more information about using HTTP headers, see Working with HTTP headers.

SOAPHEADER clause    When declaring a SOAP web service as a function, use this clause to specify one or more SOAP request header entries. A SOAP header can be declared as a static constant, or can be dynamically set using the parameter substitution mechanism (declaring IN, OUT, or INOUT parameters for hd1, hd2, and so on). A web service function can define one or more IN mode substitution parameters, but can not define an INOUT or OUT substitution parameter. For more information about how to use this clause, see the SOAPHEADER clause of the CREATE PROCEDURE statement.

For more information on using SOAP headers, see Working with SOAP headers.

TYPE clause    Used to specify the format used when making the web service request. If SOAP is specified or no type clause is included, the default type SOAP:RPC is used. HTTP implies HTTP:POST. Since SOAP requests are always sent as XML documents, HTTP:POST is always used to send SOAP requests.

NAMESPACE clause    Applies to SOAP client functions only. This clause identifies the method namespace usually required for both SOAP:RPC and SOAP:DOC requests. The SOAP server handling the request uses this namespace to interpret the names of the entities in the SOAP request message body. The namespace can be obtained from the WSDL description of the SOAP service available from the web service server. The default value is the procedure's URL, up to but not including the optional path component.

CERTIFICATE clause    To make a secure (HTTPS) request, a client must have access to the certificate used by the HTTPS server. The necessary information is specified in a string of semicolon-separated key/value pairs. The certificate can be placed in a file and the name of the file provided using the file key, or the whole certificate can be placed in a string, but not both. The following keys are available:

KeyAbbreviationDescription
fileThe file name of the certificate.
certificatecertThe certificate itself.
companycoThe company specified in the certificate.
unitThe company unit specified in the certificate.
nameThe common name specified in the certificate.

Certificates are required only for requests that are either directed to an HTTPS server, or can be redirected from a non-secure to a secure server.

CLIENTPORT clause    Identifies the port number on which the HTTP client procedure communicates using TCP/IP. It is provided for and recommended only for connections across firewalls, as firewalls filter according to the TCP/UDP port. You can specify a single port number, ranges of port numbers, or a combination of both; for example, CLIENTPORT '85,90-97'.

See ClientPort protocol option [CPORT].

PROXY clause    Specifies the URI of a proxy server. For use when the client must access the network through a proxy. Indicates that the procedure is to connect to the proxy server and send the request to the web service through it.

Remarks

The CREATE FUNCTION statement creates a user-defined function in the database. A function can be created for another user by specifying an owner name. Subject to permissions, a user-defined function can be used in exactly the same way as other non-aggregate functions.

SQL Anywhere treats all user-defined functions as deterministic unless they are declared NOT DETERMINISTIC. Deterministic functions return a consistent result for the same parameters, and are free of side effects. That is, the database server assumes that two successive calls to the same function with the same parameters will return the same result, and will not have any unwanted side-effects on the query's semantics.

If a function returns a result set, it cannot also set output parameters or return a return value.

For web service client functions, the return type of SOAP and HTTP functions must one of the character data types, such as VARCHAR. The value returned is the body of the HTTP response. No HTTP header information is included. If more information is required, such as status information, use a procedure instead of a function.

Parameter values are passed as part of the request. The syntax used depends on the type of request. For HTTP:GET, the parameters are passed as part of the URL; for HTTP:POST requests, the values are placed in the body of the request. Parameters to SOAP requests are always bundled in the request body.

Permissions

Must have RESOURCE authority, unless creating a temporary function.

External functions, including Java functions, must have DBA authority.

Side effects

Automatic commit.

See also
Standards and compatibility
Examples

The following function concatenates a firstname string and a lastname string.

CREATE FUNCTION fullname(
   firstname CHAR(30),
   lastname CHAR(30) )
RETURNS CHAR(61)
BEGIN
   DECLARE name CHAR(61);
   SET name = firstname || ' ' || lastname;
   RETURN (name);
END;

The following examples illustrate the use of the fullname function.

Return a full name from two supplied strings:

SELECT fullname ( 'joe', 'smith' );
fullname('joe', 'smith')
joe smith

List the names of all employees:

SELECT fullname ( GivenName, Surname )
FROM Employees;
fullname (GivenName, Surname)
Fran Whitney
Matthew Cobb
Philip Chin
Julie Jordan
...

The following function uses Transact-SQL syntax:

CREATE FUNCTION DoubleIt( @Input INT )
RETURNS INT
AS
  DECLARE @Result INT
  SELECT @Result = @Input * 2
  RETURN @Result

The statement SELECT DoubleIt( 5 ) returns a value of 10.

The following statement creates an external function written in Java:

CREATE FUNCTION encrypt( IN name char(254) )
RETURNS VARCHAR
EXTERNAL NAME
  'Scramble.encrypt (Ljava/lang/String;)Ljava/lang/String;'
LANGUAGE JAVA;