Explain the difference between a primary key and an alternate key in indexed file processing.
- Primary key allows duplicate values, while alternate key enforces uniqueness.
- Primary key is the default key, and alternate key is used for backup purposes.
- Primary key is used for sorting records in ascending order. Alternate key is the main key used for retrieval.
- Primary key uniquely identifies records and determines the file's physical order. Alternate key provides an alternative access path and can have duplicates.
In indexed file processing, a primary key uniquely identifies records and establishes the file's physical order. An alternate key provides an alternative access path without affecting the physical order and can have duplicate values.
How does the "WORKING-STORAGE SECTION" differ from the "LINKAGE SECTION" in COBOL?
- Working-Storage is used for data validation, while Linkage is used for data transformation
- Working-Storage is used for global variables, while Linkage is used for local variables
- Working-Storage is used for input data, while Linkage is used for output data
- Working-Storage is used for temporary storage within the program, while Linkage is used for communication between programs
The "WORKING-STORAGE SECTION" in COBOL is used for declaring variables that are used for temporary storage within the program. In contrast, the "LINKAGE SECTION" is used for communication between programs, passing data from one program to another.
You are developing a COBOL application that needs to retrieve customer information from a database. Which SQL statement should you use for this purpose?
- EXEC SQL DELETE
- EXEC SQL INSERT
- EXEC SQL SELECT
- EXEC SQL UPDATE
To retrieve data from a database in COBOL, you would use the EXEC SQL SELECT statement. This statement is used to query the database and retrieve specific information, such as customer details, based on the specified conditions.
In COBOL, the OCCURS clause can be used to define a group data item with a ________ number of occurrences.
- Dynamic
- Fixed
- Limited
- Variable
The OCCURS clause in COBOL is used to define a group data item with a variable number of occurrences. It allows you to create arrays or tables with a dynamic size, providing flexibility in handling data elements.
In the context of indexed file processing, what does an alternate index provide?
- A backup index used in case of index corruption
- A secondary copy of the primary index for redundancy
- An additional path to access records based on a different key, improving retrieval efficiency
- An alternative record layout for specialized queries
An alternate index in indexed file processing provides an additional path to access records based on a different key. This enhances retrieval efficiency by allowing applications to access the same data using different indexing criteria.
What is the purpose of the AFTER clause in a PERFORM statement?
- To define the conditions for loop termination
- To execute a block of code before entering the loop
- To indicate the starting point for loop execution
- To specify actions after the loop execution
The AFTER clause in a PERFORM statement is used to specify actions that should be performed after the completion of the loop. It allows you to define statements that will be executed once the loop has finished its iterations.
In COBOL, _____ is commonly used for maintaining and accessing indexed files.
- ACCESS MODE IS RANDOM
- ACCESS MODE IS SEQUENTIAL
- FILE STATUS IS _______
- RECORD KEY IS _______
In COBOL, the "ACCESS MODE IS RANDOM" clause is commonly used for maintaining and accessing indexed files. This access mode allows random access to records based on the specified record key.
In COBOL, when is the EXIT statement typically used for error handling?
- At the end of every COBOL program
- To terminate the program gracefully
- When an abnormal condition occurs during program execution
- When performing arithmetic calculations
The EXIT statement in COBOL is typically used for error handling when an abnormal condition occurs during program execution. It provides a mechanism to exit the program prematurely and handle exceptional situations.
Explain the purpose of the PREPARE statement in COBOL when dealing with dynamic SQL.
- The PREPARE statement is used to declare and initialize variables before using them in SQL statements.
- The PREPARE statement is used to define the structure of the database tables in COBOL programs.
- The PREPARE statement is used to execute SQL statements directly in COBOL programs.
- The PREPARE statement is used to validate SQL syntax and create an execution plan without executing the statement immediately. This is particularly useful in dynamic SQL scenarios where the SQL statement is not known until runtime.
In dynamic SQL, the PREPARE statement in COBOL is used to validate SQL syntax and create an execution plan without immediate execution. It allows for flexibility when the SQL statement is determined at runtime.
The "EVALUATE" statement in COBOL is particularly useful when you have to evaluate multiple _____ in your program.
- Conditions
- Expressions
- Statements
- Variables
The "EVALUATE" statement in COBOL is useful when you need to evaluate multiple conditions in your program. It provides a concise and efficient way to handle multiple branches of logic based on the value of an expression or variable.