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>   CREATE FUNCTION
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><H1
>CREATE FUNCTION</H1
><DIV
CLASS="REFNAMEDIV"
><H2
>Name</H2
>   CREATE FUNCTION
   &#8212;    Defines a new function
  </DIV
><DIV
CLASS="REFSYNOPSISDIV"
><PRE
CLASS="SYNOPSIS"
>CREATE FUNCTION <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
> ( [ <TT
CLASS="REPLACEABLE"
><I
>ftype</I
></TT
> [, ...] ] )
    RETURNS <TT
CLASS="REPLACEABLE"
><I
>rtype</I
></TT
>
    AS <TT
CLASS="REPLACEABLE"
><I
>path</I
></TT
>
    LANGUAGE '<TT
CLASS="REPLACEABLE"
><I
>langname</I
></TT
>'
  </PRE
><DIV
CLASS="REFSECT2"
><H3
>    Inputs
   </H3
><P
>       <P
></P
></P><DL
><DT
><TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
></DT
><DD
><P
>           The name of a function to create.
	  </P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>ftype</I
></TT
></DT
><DD
><P
>           The data type of function arguments.
	  </P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>rtype</I
></TT
></DT
><DD
><P
>           The return data type.
	  </P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>path</I
></TT
></DT
><DD
><P
>	   May be either an SQL-query or an absolute path to an
           object file.
	  </P
></DD
><DT
><TT
CLASS="REPLACEABLE"
><I
>langname</I
></TT
></DT
><DD
><P
>           may be '<TT
CLASS="LITERAL"
>C</TT
>', '<TT
CLASS="LITERAL"
>sql</TT
>',
 '<TT
CLASS="LITERAL"
>internal</TT
>'
 or '<TT
CLASS="REPLACEABLE"
><I
>plname</I
></TT
>',
 where '<TT
CLASS="REPLACEABLE"
><I
>plname</I
></TT
>'
 is the name of a created procedural
           language. See <B
CLASS="COMMAND"
>CREATE LANGUAGE</B
> for details.
	  </P
></DD
></DL
><P>
  </P
></DIV
><DIV
CLASS="REFSECT2"
><H3
>    Outputs
   </H3
><P
>&#13;       <P
></P
></P><DL
><DT
><SPAN
CLASS="RETURNVALUE"
>CREATE</SPAN
></DT
><DD
><P
>	   This is returned if the command completes successfully.
   </P
></DD
></DL
><P>
  </P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><H2
>   Description
  </H2
><P
>   <B
CLASS="COMMAND"
>CREATE FUNCTION</B
> allows a
<SPAN
CLASS="PRODUCTNAME"
>Postgres</SPAN
> user
to register a function
   with a database. Subsequently, this user is treated as the
   owner of the function.
  </P
><DIV
CLASS="REFSECT2"
><H3
>    Notes
   </H3
><P
>    Refer to the chapter on functions 
in the <I
CLASS="CITETITLE"
>PostgreSQL Programmer's Guide</I
>
 for further information.
   </P
><P
>    Use <B
CLASS="COMMAND"
>DROP FUNCTION</B
>
    to drop user-defined functions.
   </P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><H2
>   Usage
  </H2
><P
>   To create a simple SQL function:
  </P
><PRE
CLASS="PROGRAMLISTING"
>CREATE FUNCTION one() RETURNS int4
    AS 'SELECT 1 AS RESULT'
    LANGUAGE 'sql';

SELECT one() AS answer;

<TT
CLASS="COMPUTEROUTPUT"
>answer 
------
1</TT
>
  </PRE
><P
>   To create a C function, calling a routine from a user-created
   shared library.  This particular routine calculates a check
   digit and returns TRUE if the check digit in the function parameters
   is correct. It is intended for use in a CHECK contraint.
  </P
><PRE
CLASS="PROGRAMLISTING"
><TT
CLASS="USERINPUT"
><B
>CREATE FUNCTION ean_checkdigit(bpchar, bpchar) RETURNS bool
    AS '/usr1/proj/bray/sql/funcs.so' LANGUAGE 'c';

CREATE TABLE product
(
     id              char(8)         PRIMARY KEY,
     eanprefix       char(8)         CHECK (eanprefix ~ '[0-9]{2}-[0-9]{5}')
                                     REFERENCES brandname(ean_prefix),
     eancode         char(6)         CHECK (eancode ~ '[0-9]{6}'),
     CONSTRAINT ean CHECK (ean_checkdigit(eanprefix, eancode))
);</B
></TT
>
  </PRE
></DIV
><DIV
CLASS="REFSECT1"
><H2
>   Bugs
  </H2
><P
>   A C function cannot return a set of values.
  </P
></DIV
><DIV
CLASS="REFSECT1"
><H2
>   Compatibility
  </H2
><P
>    <B
CLASS="COMMAND"
>CREATE FUNCTION</B
> is
 a <SPAN
CLASS="PRODUCTNAME"
>Postgres</SPAN
> language extension.
   </P
><DIV
CLASS="REFSECT2"
><H3
>    SQL/PSM
   </H3
><P
>&#13;<BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>      PSM stands for Persistent Stored Modules. It is a procedural
      language and it was originally hoped that PSM would be ratified
      as an official standard by late 1996. As of mid-1998, this
has not yet happened, but it is hoped that PSM will
      eventually become a standard.
     </P
></BLOCKQUOTE
>

SQL/PSM <B
CLASS="COMMAND"
>CREATE FUNCTION</B
> has the following syntax:
<PRE
CLASS="SYNOPSIS"
>CREATE FUNCTION <TT
CLASS="REPLACEABLE"
><I
>name</I
></TT
>
    ( [ [ IN | OUT | INOUT ] <TT
CLASS="REPLACEABLE"
><I
>parm</I
></TT
> <TT
CLASS="REPLACEABLE"
><I
>type</I
></TT
> [, ...] ] )
     RETURNS <TT
CLASS="REPLACEABLE"
><I
>rtype</I
></TT
>
     LANGUAGE '<TT
CLASS="REPLACEABLE"
><I
>langname</I
></TT
>'
     ESPECIFIC <TT
CLASS="REPLACEABLE"
><I
>routine</I
></TT
>
     <TT
CLASS="REPLACEABLE"
><I
>SQL-statement</I
></TT
></PRE
>

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