NCLOB

NCLOB, or National Character Large Object, is a data type used to store large amounts of Unicode text. It holds data in the database’s national character set, which is distinct from the database’s primary character set. This enables full Unicode support for multilingual data and can simplify handling text that may not be representable in the database’s main character set.

NCLOB is typically contrasted with CLOB, which stores large text using the database character set. If the database character set cannot represent certain characters, NCLOB provides an alternative path by relying on the national character set. This can reduce character set conversion issues when data originates from diverse languages and scripts.

Storage and limits for NCLOBs are generally up to 4 gigabytes of data. The exact number of characters is dependent on the encoding of the national character set in use; some encodings use more bytes per character than others. As with other LOB types, NCLOB data is stored outside the main table row and accessed via LOB APIs.

Usage commonly involves defining a table column as NCLOB, for example, content NCLOB. Inserting Unicode text may require national-character literals (for instance, using a prefix such as N'…' for Unicode literals). Applications interact with NCLOB values through standard LOB operations and functions, such as reading, writing, and substring operations, with consideration for potential performance implications on large objects.

NCLOB is an Oracle-oriented term and is not universally available under the same name in all RDBMS. Some systems offer equivalent functionality under NVARCHAR2, NCLOB-like types, or through Unicode-enabled LOB features.