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Oracle PL/SQL is a dynamic, robust programming language that offers modern features to develop efficient, smooth applications. Often compared to Microsoft’s T-SQL, PL/SQL adds procedures and functions to standard SQL enhancing database applications’ capability. Given its transaction processing strength, it is an ideal choice for running complex computations and heavy data manipulations.

Overview of PL/SQL

PL/SQL is a procedural extension of SQL, which creates a natural, efficient, and safe programming environment. It fully supports SQL data manipulation and enhances it by allowing saved procedures and functions, better error handling, and robust standards not typically available in SQL.

PL/SQL is block structured, and each anonymous block or subprogram has an optional declaration section where all the variables, cursors, user-defined exceptions, and subprograms are declared. Furthermore, PL/SQL being a procedural language, supports iteration, conditional branching, and allows re-usability via user-defined subprograms.

Solving a Problem with PL/SQL

Here we will write a PL/SQL block that solves a common problem: retrieving information from database tables with possible exceptions.

First, we need to declare the variables to hold the data retrieved from the database. In PL/SQL, we declare variables in the declaration section of a block.

  l_name    employees.last_name%TYPE;
  l_salary  employees.salary%TYPE;
  l_emp_id  employees.employee_id%TYPE := &Emp_Id;

The main action happens in the execution section:

  SELECT last_name, salary
    INTO l_name, l_salary
    FROM employees
   WHERE employee_id = l_emp_id;
  DBMS_OUTPUT.PUT_LINE('Name: ' || l_name);
  DBMS_OUTPUT.PUT_LINE('Salary: ' || l_salary);
    DBMS_OUTPUT.PUT_LINE('No employee found with ID: ' || l_emp_id);
    DBMS_OUTPUT.PUT_LINE('Error occurred: ' || SQLCODE || ' - ' || SQLERRM);

Importance of Error Handling

Effective error handling in PL/SQL applications can help significantly reduce debugging time and improve the application’s robustness.

In the script above, we have handled the possibility of an exception (an error). If the specified Employee ID does not exist – the SELECT INTO statement raises a NO_DATA_FOUND exception. If any other exception gets raised, the OTHERS handler catches it.

This form of exception handling is a prime example of PL/SQL’s robustness and capability in managing the control flow of the application.

PL/SQL Libraries and Packages

PL/SQL allows the use of pre-defined SQL packages that help solve common problems. For example, the DBMS_OUTPUT package was used in the previous example to output the data to the console.

There are many more similar packages like DBMS_SQL (dynamic SQL), UTL_FILE (handling server-side files), UTL_MAIL (sending emails from PL/SQL), etc. These packages, combined with the strong procedural language features of PL/SQL, offer robust capabilities for developing powerful database applications.

Advantages of PL/SQL

Some key advantages of PL/SQL include its support for SQL, its portability, security, and excellent performance. Due to its close integration with SQL, you can use all SQL data types and all SQL functions and operators.

It enhances productivity by providing advanced features such as exception handling, encapsulation, data hiding, and inheritance. PL/SQL also supports cursors, which are named memory areas for manipulating complex SQL queries’ output.

With PL/SQL, you can protect your data from unauthorized users by implementing strong security policies. It also has support for both static and dynamic SQL, further boosting its capability.

PL/SQL also offers excellent performance by allowing bundling of SQL statements into a single block that can be sent to the database server in a single call. This reduces network traffic and enhances the execution speed of the application.

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