Level Up Your Oracle Skills: Mastering Boolean Data Representation

Prior to Oracle Database 23c (released in 2023), Oracle databases did not have a dedicated boolean data type for storing true/false values in columns. However, there were various workarounds commonly used:

1. Numeric Representation (NUMBER):

   • A single-digit number (typically 0 for false and 1 for true) was used in a NUMBER column.
   • Check constraints could be enforced to ensure values were only 0 or 1.

2. Character Representation (CHAR, VARCHAR2):

   • Single-character strings like 'Y'/'N' or 'true'/'false' were stored in CHAR or VARCHAR2 columns.
   • Custom logic or constraints might be needed to interpret these values correctly.

Limitations of Workarounds:

• Less Intuitive: These methods weren't as clear and self-documenting as a dedicated boolean type.
• Potential for Errors: Incorrect data could be accidentally inserted if not carefully handled.
• Inconsistency: Different developers might use different approaches, leading to less maintainable code.

New Boolean Data Type (Oracle Database 23c and Later):

Starting with Oracle Database 23c, a native BOOLEAN data type was introduced. This provides:

• Clarity: Code becomes more readable and easier to understand, as BOOLEAN columns explicitly represent true/false values.
• Improved Data Integrity: The database enforces that only valid boolean values can be stored.
• Standardization: A consistent way to represent boolean data is established.

To create a column with the BOOLEAN data type:

CREATE TABLE my_table (
  is_active BOOLEAN
);

Inserting data:

INSERT INTO my_table (is_active) VALUES (TRUE);

Summary:

• Prior to Oracle Database 23c, workarounds were used to represent boolean data.
• Oracle Database 23c (and later) offers a dedicated BOOLEAN data type for clarity, data integrity, and standardization.

Example Codes for Representing Boolean Data in Oracle

Pre-23c Workarounds:

Using a NUMBER (1 for true, 0 for false):

CREATE TABLE users (
  id NUMBER PRIMARY KEY,
  is_admin NUMBER(1) CHECK (is_admin IN (0, 1)) DEFAULT 0
);

INSERT INTO users (id, is_admin) VALUES (1, 1);  -- Inserting a user as admin

SELECT id, CASE WHEN is_admin = 1 THEN 'Admin' ELSE 'Regular User' END AS user_type
FROM users;

In this example:

• The is_admin column is a NUMBER(1) to limit values to 0 or 1.
• A check constraint ensures only valid values are inserted.
• The CASE expression translates the numeric value to a more readable string for user display.

Using a Character String (Y/N for true/false):

CREATE TABLE products (
  product_id NUMBER PRIMARY KEY,
  is_available CHAR(1) CHECK (is_available IN ('Y', 'N')) DEFAULT 'N'
);

INSERT INTO products (product_id, is_available) VALUES (101, 'Y');

SELECT product_id, is_available
FROM products
WHERE is_available = 'Y'; -- Find available products

• The is_available column is a CHAR(1) to store a single character.
• A check constraint limits values to 'Y' or 'N'.
• The query directly compares the character value for filtering.

CREATE TABLE orders (
  order_id NUMBER PRIMARY KEY,
  is_shipped BOOLEAN DEFAULT FALSE
);

INSERT INTO orders (order_id, is_shipped) VALUES (2023, TRUE);

SELECT order_id, is_shipped
FROM orders
WHERE is_shipped = TRUE; -- Find shipped orders

Here, the is_shipped column is explicitly defined as BOOLEAN, providing:

• Clear representation of true/false values.
• Automatic data integrity checks by the database.

• This approach leverages the underlying storage capabilities of Oracle.
• A single-bit column (often part of a larger byte or integer) can be used to represent true/false.
• Setting the bit to 1 signifies true, and 0 signifies false.
• This method requires significant custom logic in PL/SQL to manipulate and interpret the bit value. It's generally not recommended due to its complexity and lack of readability for most developers.

Using a User-Defined Type (UDT):

• You can create a UDT with two attributes, one named TRUE (of any data type) and another named FALSE.
• A single record instance of the UDT would then represent either TRUE or FALSE depending on which attribute has a value.
• This method offers more flexibility but adds complexity to code and database management.

Leveraging Existing Flag Columns:

• If you already have a column with limited values (e.g., 'active'/'inactive') that essentially functions as a boolean flag, you might choose to continue using it for backward compatibility or simplicity.
• However, this approach lacks clarity and may not be ideal for new development.

Choosing the Right Method:

When selecting a method for pre-23c Oracle databases, consider the following factors:

• Readability and Maintainability: Opt for methods that are clear and easy for developers to understand and modify.
• Data Integrity: If strict enforcement of true/false values is crucial, consider check constraints or custom validation logic.
• Performance: For high-performance applications, using a numeric representation might be slightly faster, but the difference is often negligible compared to other factors.