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From: marc@sei.cmu.edu (Marc Graham)
Newsgroups: comp.databases
Subject: Re: c++ and SQL
Message-ID: <26540@as0c.sei.cmu.edu>
Date: 5 Jun 91 15:58:01 GMT
References: <AV.91May28113952@kielo.uta.fi> <CIMSHOP!DAVIDM.91Jun2195536@uunet.UU.NET>
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Organization: The Software Engineering Institute
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In article <CIMSHOP!DAVIDM.91Jun2195536@uunet.UU.NET>, cimshop!davidm@uunet.UU.NET (David S. Masterson) writes:

|> #define SOAPBOX_MODE
|> 
|> For this reason, I believe that the SQL standard should not specify a
|> preprocessing standard on top of some other language, but rather a method of
|> using SQL that does *not* require a change to the base language that it will
|> be used with.  If that were the standard, then any RDBMS with an SQL interface
|> that works under (for instance) VAX/VMS would be able to interface with *all*
|> the languages used on VMS.  You would not need a special preprocessor for each
|> language.
|> 
|> #undef SOAPBOX_MODE

The current ANSI SQL standard includes just such a facility. It is
called the Module Language and is defined in ANS X3H2.135-1989
and X3H2.168-1989. A module has the following format (clause 7 of
.135 and clauses 7 and 8 of .168):

-=-=-=-=-=-=-
MODULE My_Module
LANGUAGE ADA

DECLARE My_Cursor CURSOR
FOR 
SELECT stuff
FROM places
WHERE Column=Parameter

PROCEDURE Open_My_Cursor
  Parameter INT
  SQLCODE;

  OPEN My_Cursor;

-- and fetch and close statements
-=-=-=-=-=-

Notice that the only language specific part is the LANGUAGE clause,
which specifies the calling conventions to be used by the code to be
produced by the module language compiler. That code will contain a
callable procedure called Open_My_Cursor which will take an integer
input paramter called Parameter and produce an SQLCODE. And similar
things for fetch, close, and whatever else you like.

The Ada standardization group (Working Group 9 of SubCommittee 22 of
ISO) has been working on an extension (actually, a modest rewrite) to
the module language, called the SQL Ada Module Description Language
(SAMeDL) which is a module language more suitable to the needs of Ada.
(Strong, abstract types, checked at compile time, for example.) 
Marc H. Graham                    Software Engineering Institute
marc@sei.cmu.edu                  Carnegie Mellon University
(412) 268 7784                    Pittsburgh, PA   15213