Learn Oracle database character set in five minutes

There are many things worth learning about in Oracle. Here we mainly introduce the character set of Oracle databases, including the national character set. Oracle Database character set (NLS supported by national languages) is used to store, process, and retrieve data in national languages and formats. With global support, Oracle provides users with familiar database mother-tongue environments, such as date formats, digital formats, and storage sequences. Oracle supports multiple languages and character sets, while Oracle9i supports 57 languages, 88 countries, and 235 character sets.

Single-byte encoding
1. single-byte 7-bit character set, which can be 128 characters. The most common character set is US7ASCII.
2. single-byte 8-bit character set, which can be 256 characters. It is suitable for most European countries.
Example: WE8ISO8859P1 (Western Europe, 8-bit, ISO standard 8859P1 encoding)

Multi-byte encoding

1. variable-length multi-byte encoding
Some characters are represented by one byte. Other characters are represented by two or more characters. Long-length multi-byte encoding is commonly used for Asian languages, such as Japanese, Chinese, and Hindi. For example: AL32UTF8 where AL stands for ALL, that applies to ALL languages), UTF-8 is the 8-bit unicode encoding, which can represent a unicode Character in 1, 2, 3 bytes

2. Fixed Length multi-byte encoding
Each character uses a fixed length of bytes encoding scheme, currently the Oracle database character set only supports the Fixed Length of Multi-byte encoding is AL16UTF16, is also only used for the National Character Set UTF-16 is unicode 16-bit encoding method, it is a fixed-length multi-byte encoding that uses two bytes to represent a unicode character.

When creating a database, you can specify the character set and national character set ).

Character Set
(1) used to store CHAR, VARCHAR2, CLOB, LONG, and other data types
(2) used to mark table names, column names, PL/SQL variables, etc.
(3) used to store SQL and PL/SQL program units

National Character Set
(1) used to store NCHAR, NVARCHAR2, NCLOB, and other data types
(2) The National Character Set is essentially an additional character set selected for Oracle. It is mainly used to enhance the character processing capability of Oracle, the NCHAR data type can support the use of fixed-length multi-byte encoding in Asia, while the Oracle database character set cannot. Country
The delimiter set is redefined in Oracle9i. It can only be selected in AL16UTF16 and UTF8 in unicode encoding. The default value is AL16UTF16.

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