Introduction to Oracle NCLOB Data Type

In Oracle database, the NCLOB data type is used to store large amounts of character data in Unicode character set, with a maximum length of 4GB. Unlike the CLOB data type, NCLOB uses the Unicode character set and can store characters from any language, including special characters and emojis.

Syntax

The following syntax can be used to define the NCLOB data type when creating a table:

column_name NCLOB [ (max_size) ] [ LOB_parameters ]

Where max_size specifies the maximum length of the NCLOB data type, with a maximum value of 4GB.

Use Cases

Due to its support for Unicode character set, the NCLOB data type is suitable for applications that need to store characters from different languages, such as multilingual websites, internationalized software, and so on.

In addition, the NCLOB data type is also suitable for storing large text data, such as long articles, e-books, theses, and so on.

Examples

Here are two examples that demonstrate how to use the NCLOB data type.

Example 1

Using NCLOB data type to store a long article when creating a table:

CREATE TABLE articles (
   article_id NUMBER PRIMARY KEY,
   article_title VARCHAR2(200),
   article_content NCLOB
);

INSERT INTO articles (article_id, article_title, article_content)
VALUES (1, 'Getting Started with Oracle', 'Oracle Database is a relational database management system...');

In this example, the NCLOB data type is used to store the content of the article_content column, which stores the body of the article, with a length of up to 4GB.

Example 2

Using NCLOB data type to store multilingual text data when creating a table:

CREATE TABLE messages (
   message_id NUMBER PRIMARY KEY,
   language_code VARCHAR2(10),
   message_text NCLOB
);

INSERT INTO messages (message_id, language_code, message_text)
VALUES (1, 'zh_CN', '欢迎访问我们的网站。');
INSERT INTO messages (message_id, language_code, message_text)
VALUES (2, 'en_US', 'Welcome to our website.');

In this example, the NCLOB data type is used to store the content of the message_text column, which stores multilingual text data, with a length of up to 4GB.

Conclusion

The NCLOB data type is a type in Oracle database used to store large amounts of character data in Unicode character set, with a maximum length of 4GB. It is suitable for applications that need to store characters from different languages and large text data. The NCLOB data type can be used to define columns when creating tables.