What Is a CLOB Data Type?


Heather Bennett

The CLOB (Character Large Object) data type is a type of data storage in databases that allows for the storage of large amounts of character data. It is commonly used to store text documents, such as articles, blog posts, or even entire books.

What is a CLOB?

A CLOB is a data type that can store large amounts of character data, typically up to 4 gigabytes. It is similar to the VARCHAR or TEXT data types, but with a much larger capacity.

Unlike VARCHAR or TEXT, which have a fixed maximum length, a CLOB can store variable-length character data without any predefined limit. This makes it ideal for storing large blocks of text or other character-based data.

Why use a CLOB?

There are several reasons why you might choose to use a CLOB data type:

  • Storage: If you need to store large amounts of text or character-based data, a CLOB offers an efficient and convenient solution.
  • Flexibility: Unlike fixed-length data types like CHAR or VARCHAR, a CLOB can store variable-length data without any predefined limit.
  • Performance: While storing and retrieving large amounts of data may take longer compared to smaller datatypes, modern databases optimized for handling CLOBs can still provide good performance.

CLOB implementation

The implementation of the CLOB data type may vary depending on the database management system (DBMS) you are using. However, most DBMSs provide native support for CLOBs and offer specific functions and operators for working with this datatype.

In SQL, you can create a table with a CLOB column using the following syntax:

CREATE TABLE my_table (
  clob_column CLOB

To insert data into a CLOB column, you can use the INSERT statement with the appropriate data type:

INSERT INTO my_table (clob_column)
VALUES ('This is a large block of text');

To retrieve the data from a CLOB column, you can use the SELECT statement:

SELECT clob_column
FROM my_table;


The CLOB data type is a powerful tool for storing and managing large amounts of character-based data. It offers flexibility, efficiency, and convenience for applications that require handling extensive text documents or other character-based information.

By understanding how to use the CLOB datatype effectively, you can make your database more versatile and capable of handling complex textual data.

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