Mimer SQL Developers - Interface - Embedded SQL in COBOL

Embedded SQL in COBOL
Category: SQL

Introduction

Embedded SQL means that you can use SQL statements through a host programming language, C/C++, COBOL, or FORTRAN. COBOL 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 COBOL 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” and terminated by “END-EXEC”, e.g. “EXEC SQL DELETE FROM HOTEL END-EXEC”.

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.eco (see Links below).


       IDENTIFICATION DIVISION.
       PROGRAM-ID. SIMPLE.

       DATA DIVISION.
       WORKING-STORAGE SECTION.
           EXEC SQL BEGIN DECLARE SECTION END-EXEC.
       01  SQLSTATE     PIC X(5).
       01  TABLE-SCHEMA PIC X(128).
       01  TABLE-NAME   PIC X(128).
       01  TABLE-TYPE   PIC X(20).
           EXEC SQL END DECLARE SECTION END-EXEC.

       PROCEDURE DIVISION.
       MAIN SECTION.

       DO-IT.
           EXEC SQL DECLARE MYCURSOR CURSOR FOR
                    SELECT TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE
                    FROM INFORMATION_SCHEMA.TABLES END-EXEC.

      *    Connect to default database
           EXEC SQL CONNECT TO ''
                    USER 'SYSADM' USING 'SYSADM' END-EXEC.

           EXEC SQL OPEN MYCURSOR END-EXEC.

           PERFORM FETCH-AND-DISPLAY UNTIL SQLSTATE = "02000".

           EXEC SQL CLOSE MYCURSOR END-EXEC.
           EXEC SQL COMMIT END-EXEC.
           EXEC SQL DISCONNECT DEFAULT END-EXEC.
           STOP RUN.

       FETCH-AND-DISPLAY.
           EXEC SQL FETCH MYCURSOR INTO :TABLE-SCHEMA,
                                        :TABLE-NAME,
                                        :TABLE-TYPE END-EXEC.
           IF SQLSTATE NOT = "02000",
               DISPLAY TABLE-SCHEMA, TABLE-NAME, TABLE-TYPE.

       END PROGRAM SIMPLE.

The program is preprocessed as follows:

esql –cob simple.eco

The resulting file, ‘simple.cob’, is compiled using a COBOL-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 distributed example program example.eco

Benefits

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

Links

Program example: example.eco

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