HP 3000 Manuals

ALLBASE/SQL FORTRAN Application Programming Guide

The ALLBASE/SQL FORTRAN Preprocessor 

The FORTRAN preprocessor that is part of ALLBASE/SQL is specifically for
FORTRAN 77 programs.  Although the preprocessor ignores FORTRAN
statements in your source code, it generates FORTRAN statements, based on
embedded SQL commands.

Figure 1-2  summarizes the four main preprocess-time events:

   *   Syntax checking of SQL commands and host variable declarations.

   *   Creation of compilable files:  one modified source code file and
       one include file.

   *   Creation of an installable module.

   *   Storage of a module in the system catalog.


          Figure 1-2.  Preprocess-Time Events 

Effect of Preprocessing on Source Code 

The FORTRAN preprocessor scans the source code for SQL commands.  If the
syntax of an SQL command is valid, the preprocessor converts the command
to compilable FORTRAN statements that call ALLBASE/SQL external
procedures at runtime.  During preprocessing, for example, the SQL
command:

EXEC SQL SELECT PartNumber, PartName, SalesPrice 1 INTO :PartNumber, 2 
:PartName, 3 :SalesPrice 4 FROM Purchdb.Parts 5 WHERE PartNumber = 
:PartNumber 

is converted into the following modified source code statements:

     C**** Start SQL Preprocessor ****
     C           EXEC SQL SELECT  PartNumber, PartName, SalesPrice
     C    1                 INTO :PartNumber,
     C    2                      :PartName,
     C    3                      :SalesPrice :SalesPriceInd
     C    4                 FROM  PurchDB.Parts
     C    5                WHERE  PartNumber = :PartNumber
     C
     C**** Start Inserted Statements ****
           WRITE(SQLTMP,'(A16)')PartNumber
           CALL SQLXFE(SQLCAID,SQLOWN,SQLMDN,1,SQLTMP,16,56,1)
           IF (SQLCODE .EQ. 0) THEN
           READ(SQLTMP,'(A16,A30,A8,A2)')PartNumber,PartName,SalesPrice,Sales
          1PriceInd
           ELSE
           END IF
     C**** End SQL Preprocessor   ****

The embedded SELECT command has been converted into a FORTRAN comment,
and FORTRAN statements that enable ALLBASE/SQL to execute the SELECT
command at runtime have been inserted.  The names that appear in the
inserted FORTRAN code (italicized in the above example) identify
variables used by the ALLBASE/SQL external procedures; in this example,
the names identify variables used by the SQLXFE external procedure.  Some
of these variables are derived from host variables.  As shown in the
embedded SELECT command above, you precede a host variable with a colon
when you use it in SQL commands:

           :PartNumber

Type declarations used by preprocessor generated code are defined and
initialized in the include file the preprocessor creates.  The
preprocessor inserts INCLUDE statements that reference this file in each
program unit of the modified source code after the host variable
declarations.  Even if you do not declare host variables you must still
include the EXEC SQL BEGIN DECLARE SECTION and EXEC SQL END DECLARE
SECTION commands in order for the preprocessor to create and insert this
include file:

            INCLUDE 'SQLVAR'


CAUTION  Never modify the statements inserted by the preprocessor in the
         modified source code file, or the include file the preprocessor
         creates.  Changes to preprocessor generated information could
         damage your DBEnvironment or your system.


Effect of Preprocessing on DBEnvironments 

When you invoke the preprocessor, you name an ALLBASE/SQL DBEnvironment.
The preprocessor starts a DBE session for that DBEnvironment when
preprocessing begins and terminates that session when preprocessing ends.

When the preprocessor encounters a syntactically correct SQL command, it
creates a section and stores that section in the system catalog of the
DBEnvironment being accessed.  An ALLBASE/SQL section is a group of
stored ALLBASE/SQL instructions for executing one SQL command.

All sections created during a preprocessing session constitute a module.
The preprocessor derives the name of the module from the PROGRAM
statement or subroutine name unless you supply a different name when you
invoke the preprocessor:

     :RUN PSQLFOR.PUB.SYS;INFO = "DBEnvironmentName (MODULE(ModuleName))" 

When the preprocessor terminates its DBEnvironment session, it issues a
COMMIT WORK command if it encountered no errors.  Created sections are
stored in the system catalog and associated with the module name.

MPE/iX 5.0 Documentation