PL/SQL User’s Guide and Reference - Phần 2

National Character Types The widely used one-byte ASCII and EBCDIC character sets are adequate to represent the Roman alphabet, but some Asian languages, such as Japanese, contain thousands of characters. These languages require two or three bytes to represent each character. How does Oracle deal with such dissimilar languages? Oracle provides National Language Support (NLS), which lets you process single-byte and multi-byte character data and convert between character sets. It also lets your applications run in different language environments. With NLS, number and date formats adapt automatically to the language conventions specified for a user session. Thus, NLS allows users around the world to interact with Oracle in their native languages. PL/SQL supports two character sets called the database character set, which is used for identifiers and source code, and the national character set, which is used for NLS data. The datatypes NCHAR and NVARCHAR2 store character strings formed from the national character set. Note: When converting CHAR or VARCHAR2 data between databases with different character sets, make sure the data consists of well-formed strings. For more information, see Oracle8i National Language Support Guide.