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Embedded SQL in FORTRAN
Category: SQL
Introduction

Embedded SQL means that you can use SQL statements through a host programming language, C/C++, COBOL, and FORTRAN. FORTRAN is used as an example in this article.

You include SQL statements as part of the source code for an application. The source code is compiled and linked with the appropriate language-specific facilities. The SQL statements are executed in the context of the application.

Mimer SQL supports embedded SQL for FORTRAN according to the ISO standard.

Function

The ESQL preprocessor processes SQL statements embedded in the host language. SQL statements are identified by the leading delimiter “EXEC SQL”, e.g. “EXEC SQL DELETE FROM HOTEL”.

You must declare host variables used in SQL statements within the SQL DECLARE SECTION, delimited by the statements BEGIN DECLARE SECTION and END DECLARE SECTION.

You can find detailed information on Embedded SQL in Mimer SQL Documentation Set, PDF-file. (See the Programmer's Manual.)

Example

The following is an example that connects to the database defined as the default. All rows are then fetched from the table INFORMATION_SCHEMA.TABLES.
The example is stored in a file called simple.efo (see links below).

PROGRAM SQLEX

EXEC SQL BEGIN DECLARE SECTION
CHARACTER*5 SQLSTATE
CHARACTER*128 SCHEMA
CHARACTER*128 TABLE
CHARACTER*20 TYPE
EXEC SQL END DECLARE SECTION

EXEC SQL DECLARE MYCURSOR CURSOR FOR
+ SELECT TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE
+ FROM INFORMATION_SCHEMA.TABLES

C Connect to default database
EXEC SQL CONNECT TO '' USER 'SYSADM' USING 'SYSADM'

EXEC SQL OPEN MYCURSOR

EXEC SQL FETCH MYCURSOR INTO :SCHEMA, :TABLE, :TYPE
DO WHILE (SQLSTATE .NE. ‘02000’)
WRITE(6,100) SCHEMA, TABLE, TYPE
100 FORMAT(X,A,X,A,X,A)
EXEC SQL FETCH MYCURSOR INTO :SCHEMA, :TABLE, :TYPE
END DO

EXEC SQL CLOSE MYCURSOR
EXEC SQL COMMIT
EXEC SQL DISCONNECT DEFAULT
END


The program is preprocessed as follows:

esql –for simple.efo

The resulting file, ‘simple.for’, is compiled using a FORTRAN-compiler and then linked. When executing the resulting ‘simple’ program, a list of the items selected will be displayed.

You can find a more complete example in example.efo.

Benefits

Embedded SQL is a straightforward way of writing applications that access databases.

Links

Program example: example.efo

Mimer SQL Documentation Set, PDF-file. (See the Programmer's Manual.)

Mimer SQL Documentation Set, html navigation. (See the Programmer's Manual.)

Last updated: 2002-08-21

 

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