[BUG] JSQLParser 5.4-SNAPSHOT : MySQL : charset introducer (_utf8mb4) with COLLATE not supported #2427

Failing SQL Feature

MySQL charset introducer _utf8mb4 used with COLLATE on string literals.

MySQL allows specifying a character set directly on string literals using introducers like _utf8mb4, _latin1, _binary. This can be combined with COLLATE to explicitly define collation for the literal.

SQL Example

DROP TABLE IF EXISTS custom_strings;
CREATE TABLE custom_strings (
    custom_string VARCHAR(255)
    CHARACTER SET utf8mb4
    COLLATE utf8mb4_unicode_ci
);

INSERT INTO custom_strings (custom_string) VALUES ('some text');

SELECT _utf8mb4'some text' COLLATE utf8mb4_unicode_ci AS custom_string;

Parsing Error

ParseException: Encountered: <K_COLLATE> / "COLLATE", at line 1, column 28, in lexical state DEFAULT.