PL/SQL | User Input

In PL/SQL, direct user input is typically not captured the way traditional programming languages like Java or Python do, since PL/SQL is primarily designed for server-side processing inside an Oracle database. However, there are some scenarios in which user input might be taken into consideration:

SQL*Plus or SQLcl: When working with the command-line interfaces for Oracle, you can use substitution variables to capture user input.
```
DEFINE user_input = 'Default Value';

PROMPT Enter a value:
ACCEPT user_input CHAR PROMPT 'User Input:  '

DECLARE
  v_input VARCHAR2(100);
BEGIN
  v_input := '&user_input';
  DBMS_OUTPUT.PUT_LINE('You entered: ' || v_input);
END;
/
```
Here, the ACCEPT command captures user input into the user_input variable, which is then referenced in the PL/SQL block using &user_input.
Oracle APEX (Application Express): In Oracle's low-code development platform, you can design web-based forms that capture user input, which can then be processed by PL/SQL.
External Applications: When building applications (in Java, C#, Python, etc.) that interface with an Oracle database, user input can be captured by the application and then passed to PL/SQL procedures and functions via parameters.
Oracle Forms: A GUI-based tool that allows you to build enterprise applications which capture user input and interact with an Oracle database.

When dealing with user input, especially in scenarios where the input is used to construct dynamic SQL or PL/SQL, it's critically important to be cautious of SQL injection attacks. Always validate and sanitize user input and consider using bind variables or Oracle's built-in features for dynamic SQL to ensure that your operations are safe.

How to get user input in PL/SQL:

Retrieve user input in PL/SQL using the ACCEPT command.

ACCEPT user_input CHAR PROMPT 'Enter a value: ';

DECLARE
    v_user_input VARCHAR2(50);
BEGIN
    v_user_input := '&user_input';
    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/

Accepting user input in PL/SQL procedures:

Accept user input within a PL/SQL procedure.

CREATE OR REPLACE PROCEDURE get_user_input AS
    v_user_input VARCHAR2(50);
BEGIN
    ACCEPT v_user_input CHAR PROMPT 'Enter a value: ';

    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/

Using INPUT and ACCEPT in PL/SQL:

Use INPUT and ACCEPT for interactive user input in PL/SQL.

ACCEPT user_input CHAR INPUT 'Enter a value: ';

DECLARE
    v_user_input VARCHAR2(50);
BEGIN
    v_user_input := '&user_input';
    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/

Handling user input errors in PL/SQL:

Implement error handling for user input in PL/SQL.

DECLARE
    v_user_input NUMBER;
BEGIN
    BEGIN
        ACCEPT v_user_input NUMBER PROMPT 'Enter a number: ';
    EXCEPTION
        WHEN VALUE_ERROR THEN
            DBMS_OUTPUT.PUT_LINE('Invalid input. Please enter a number.');
            RAISE;
    END;

    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/

Reading user input from the command line in PL/SQL:

Read user input from the command line in PL/SQL using ACCEPT.

ACCEPT user_input CHAR FORMAT '/';

DECLARE
    v_user_input VARCHAR2(50);
BEGIN
    v_user_input := '&user_input';
    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/

PL/SQL prompt for user input:

Prompt the user for input in PL/SQL using ACCEPT.

ACCEPT user_input CHAR PROMPT 'Enter a value: ';

DECLARE
    v_user_input VARCHAR2(50);
BEGIN
    v_user_input := '&user_input';
    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/

Retrieving and validating user input in PL/SQL:

Retrieve and validate user input in PL/SQL.

DECLARE
    v_user_input VARCHAR2(50);
BEGIN
    ACCEPT v_user_input CHAR PROMPT 'Enter a value: ';

    IF v_user_input IS NOT NULL AND LENGTH(v_user_input) <= 50 THEN
        DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
    ELSE
        DBMS_OUTPUT.PUT_LINE('Invalid input.');
    END IF;
END;
/

Using DBMS_OUTPUT.PUT_LINE for user prompts in PL/SQL:

Utilize DBMS_OUTPUT.PUT_LINE for displaying prompts based on user input.

DECLARE
    v_user_input VARCHAR2(50);
BEGIN
    ACCEPT v_user_input CHAR PROMPT 'Enter a value: ';

    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/

Input validation techniques in PL/SQL:

Implement various input validation techniques in PL/SQL.

DECLARE
    v_user_input VARCHAR2(50);
BEGIN
    ACCEPT v_user_input CHAR PROMPT 'Enter a value: ';

    -- Apply validation logic here...

    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/

Dynamic SQL with user input in PL/SQL:

Use dynamic SQL with user input in PL/SQL.

DECLARE
    v_user_input VARCHAR2(50);
    v_sql_query VARCHAR2(200);
BEGIN
    ACCEPT v_user_input CHAR PROMPT 'Enter a column name: ';
    v_sql_query := 'SELECT ' || v_user_input || ' FROM your_table';
    -- Execute dynamic SQL...
END;
/

Security considerations for user input in PL/SQL:

Consider security implications when handling user input in PL/SQL.

DECLARE
    v_user_input VARCHAR2(50);
BEGIN
    ACCEPT v_user_input CHAR PROMPT 'Enter a value: ';

    -- Validate and sanitize user input...

    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/

PL/SQL user input and data types:

Handle different data types for user input in PL/SQL.

DECLARE
    v_user_input NUMBER;
BEGIN
    ACCEPT v_user_input NUMBER PROMPT 'Enter a number: ';

    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/

User input and exception handling in PL/SQL:

Implement exception handling for user input in PL/SQL.

DECLARE
    v_user_input NUMBER;
BEGIN
    BEGIN
        ACCEPT v_user_input NUMBER PROMPT 'Enter a number: ';
    EXCEPTION
        WHEN VALUE_ERROR THEN
            DBMS_OUTPUT.PUT_LINE('Invalid input. Please enter a number.');
            RAISE;
    END;

    DBMS_OUTPUT.PUT_LINE('User Input: ' || v_user_input);
END;
/