Character Sets and Collations

A character set provides character encoding rules, and a collation provides character sorting rules. This section describes the character sets and collations in MySQL-compatible GaussDB (sql_compatibility = 'MYSQL'). The following character sets, collation rules, and syntax are supported only in MySQL-compatible mode:

For details about the character sets supported by GaussDB, see "ENCODING" in CREATE DATABASE. For details about the supported collations, see the PG_COLLATION system catalog.

Some character sets have default collations in MySQL-compatible mode. For details, see Table 1.

The character set and collations are described as follows:

• Each character set has one or more collations and has only one default collation.

• Each collation has only one associated character set.

• The sorting results of the same data using different collations may be different.

• In GaussDB, utf8mb4 and utf8 are the same character set.

• When sql_compatibility is set to 'MYSQL', the BINARY and SQL_ASCII character sets are the same.

• You are advised to select the same character set for table columns and server_encoding to avoid performance loss caused by transcoding.

GaussDB supports the following functions:

• Multiple character sets can be used to store character strings.

• Collations can be used to compare character strings.

• Database-level, schema-level, table-level, and column-level character sets and collations are supported.

  

  Character strings with different character sets and collations cannot be used in the same server, database, table, or SQL statement.

• Character Sets and Collations of the Client Connection
  
• Database-level Character Sets and Collations
  
• Schema-level Character Sets and Collations
  
• Table-level Character Sets and Collations
  
• Column-level Character Sets and Collations
  
• Character Sets and Collations of Expressions of the String Type
  
• Rules for Combining Character Sets and Collations