Stands for "Character Large Object." A CLOB is a data type used by various database management systems, including Oracle and DB2. It stores large amounts of character data, up to 4 GB in size. The CLOB data type is similar to a BLOB, but includes character encoding, which defines a character set and the way each character is represented. BLOB data, on the other hand, consists of unformatted binary data.
Common data types used for storing character data include char, varchar, and text. Some database management systems also support additional text data types such as tinytext, mediumtext, and longtext. If the standard character data types are not large enough for a certain database field, the CLOB data type may be used. Since CLOB data may be very large, some database management systems do not store the text directly in the table. Instead, the CLOB field serves as an address, which references the location of the data.
CLOBs provide a way to store unusually large amounts of text, such as an entire book or publication. However, some database programs cannot run certain text operations on CLOB fields, such SQL commands with the "LIKE" condition. Therefore, it is often better to use other character data types for smaller text values.
Updated: July 9, 2009