Character Sets and Collations of Expressions of the String Type

Each expression of the string type contains character sets and collation attributes.

In MySQL-compatible mode (sql_compatibility is set to 'MYSQL'), if b_format_version is set to '5.7' and b_format_dev_version is set to 's2', the default character sets and collations of string constants are determined by the system parameters character_set_connection and collation_connection. Otherwise, the default character set is the same as server_encoding of the database, and the default collation is default.

Character set syntax:

GaussDB does not support the character set of string constants specified by the following syntax:

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[_charset_name]'string'

Collation syntax:

You can also specify the collation for expressions of other character string types.

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EXPRESSION [COLLATE collation_name]

Parameters:

COLLATE collation_name

Collation name, which is the collation attribute of the string.

• The data type of the expression must be a data type that supports collations.
• The specified collation must be supported by the character set of the expression.

Example:

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-- Use the COLLATE statement to specify the collation.
gaussdb=# SELECT 'a' COLLATE utf8mb4_general_ci = 'A';