F421, “National character”

1. Without large objects (T046)
2. Non-standard alternatives available
3. Without the synonyms national character large object and nchar large object

National character strings are character strings with an implementation-defined character set (IV194). Thus, they don’t allow a character set clause. The general assumption is that the implementation-defined character set is Unicode.

Some SQL products have only supported Unicode in the national character string types for a while. By now, most systems use Unicode as their default character set for all character strings. Even SQL Server supports Unicode in varchar columns since the release 2019. However, there is a long story that some systems might only support the BMP of Unicode—i. e. not supporting emojis. Famous examples are MySQL/MariaDB with their utf8mb3 character set and SQL Server when using a collation without supplementary character (_SC) support.

Non-Standard Alternatives

Related

Supplementary Features

• T062, “Character length units”

Mandatory Features

• E021-01, “CHARACTER data type (including all its spellings)”

• E021-02, “CHARACTER VARYING data type (including all its spellings)”

Optional Features

• F421, “National character”

• T046, “CLOB data type”

  • T043, “Multiplier T”

  • T044, “Multiplier P”

• T081, “Optional string types maximum length”

Implementation-defined Elements

• ID069, “The implicit character maximum length when character maximum length is omitted.”

• IL042, “The maximum lengths for character string types and binary string types.”

Normative References

The types national character, national char, nchar, national character varying, national char varying, nchar varying, national character large object, nchar large object and nclob are defined in ISO/IEC 9075-2:2023 as part of the optional feature F421, “National character”. Besides the large object variants, they were already available in SQL-92 (intermediate).