What Is CHAR Data Type in Oracle?

The CHAR data type in Oracle is used to store fixed-length character strings. It is commonly used to store alphanumeric data such as names, addresses, and identification numbers. The length of a CHAR column is specified in terms of characters, and it can hold a maximum of 2000 bytes.

Advantages of using CHAR data type:

• Fixed-length storage: The CHAR data type allocates a fixed amount of storage space for each value, regardless of the actual length of the string. This can improve performance when working with large tables or when performing searches and comparisons.
• Efficient for frequently accessed columns: Since the storage space is pre-allocated, accessing CHAR columns can be faster compared to variable-length data types like VARCHAR2.

Disadvantages of using CHAR data type:

• Wasted storage space: If you have variable-length strings that are shorter than the specified length, the remaining space will be wasted.
• Padding issues: When storing variable-length strings in a fixed-length field, you need to manually pad or trim the values to match the specified length. Failure to do so may result in incorrect or unexpected results.

Examples:

To create a table with a CHAR column:

CREATE TABLE employees (
    employee_id NUMBER,
    first_name CHAR(50),
    last_name CHAR(50)
);

In this example, the ‘first_name’ and ‘last_name’ columns are defined as CHAR with a length of 50 characters each.

To insert values into a table with CHAR columns:

INSERT INTO employees (employee_id, first_name, last_name)
VALUES (1, 'John', 'Doe');

Here, we are inserting the values ‘John’ and ‘Doe’ into the ‘first_name’ and ‘last_name’ columns, respectively.

To retrieve data from a CHAR column:

SELECT first_name, last_name
FROM employees
WHERE employee_id = 1;

This query will return the first and last name of the employee with an ID of 1.

Conclusion:

The CHAR data type in Oracle is suitable for storing fixed-length character strings. While it offers advantages such as fixed-length storage and efficient access for frequently accessed columns, it also has drawbacks like wasted storage space and padding issues. It is important to consider these factors when choosing the appropriate data type for your database design.