Database Interface in COBOL Language

COBOL, a language known for its historical significance in business applications, has not been left behind in the database realm. Mod

ern COBOL allows you to seamlessly interface with databases, making it a powerful tool for managing, retrieving, and updating data. In this blog post, we will explore the concept of database interfaces in COBOL, discuss how they work, and provide a practical example to demonstrate their usage.

Understanding Database Interfaces in COBOL Language

A database interface in COBOL is a module that provides an abstraction layer between the COBOL program and a database management system (DBMS). This abstraction allows COBOL programs to interact with various databases without directly dealing with the underlying DBMS-specific intricacies. Database interfaces in COBOL offer a standardized way to perform operations like querying, updating, and managing data.

Key Components of a Database Interface in COBOL Language

Database interfaces in COBOL typically consist of the following key components:

1. Connection Management: They manage connections to the database, including establishing, maintaining, and closing connections.
2. Data Access: They provide functions to execute SQL queries, retrieve data from the database, and update data.
3. Error Handling: Database interfaces handle errors and exceptions that can occur during database operations, ensuring data integrity and application stability.
4. Data Mapping: They map data between the COBOL program’s data structures and the database tables, enabling seamless data transfer.

Example: Database Interface in COBOL

Let’s consider an example where we have a COBOL program that interfaces with a relational database to retrieve employee information. We’ll use a fictional database named “EmployeeDB” and assume a COBOL program named “EmployeeQuery” that interacts with it.

IDENTIFICATION DIVISION.
PROGRAM-ID. EmployeeQuery.

DATA DIVISION.

WORKING-STORAGE SECTION.
01 Employee-Record.
   02 Employee-ID       PIC 9(5).
   02 Employee-Name     PIC X(30).
   02 Employee-Dept     PIC X(10).

PROCEDURE DIVISION.

   EXEC SQL
      DECLARE EmployeeCursor CURSOR FOR
      SELECT EmployeeID, EmployeeName, EmployeeDept
      FROM EmployeeTable
      WHERE EmployeeDept = :Dept-Name
   END-EXEC.

   MOVE 'Sales' TO Dept-Name.

   EXEC SQL
      OPEN EmployeeCursor
   END-EXEC.

   PERFORM UNTIL SQLCODE NOT EQUAL 0
      EXEC SQL
         FETCH NEXT FROM EmployeeCursor INTO
         :Employee-ID, :Employee-Name, :Employee-Dept
      END-EXEC.
      DISPLAY "Employee ID: " Employee-ID
      DISPLAY "Employee Name: " Employee-Name
      DISPLAY "Employee Department: " Employee-Dept
   END-PERFORM.

   EXEC SQL
      CLOSE EmployeeCursor
   END-EXEC.

   STOP RUN.

In this example:

• We declare a cursor (EmployeeCursor) to define the query to retrieve employee information from the “EmployeeTable” in the “EmployeeDB” database.
• We open the cursor, execute the query, and fetch the results. The data retrieved from the database is mapped to the COBOL program’s Employee-Record.
• We display the employee information.
• Finally, we close the cursor to release database resources.