mysql 字符串反转

SELECT REVERSE('Hello, World!') AS reversed_string;

+---------------------+
| reversed_string     |
+---------------------+
| !dlroW ,olleH       |
+---------------------+

DELIMITER $$

CREATE FUNCTION ReverseString(str VARCHAR(255)) RETURNS VARCHAR(255)
BEGIN
    DECLARE reversed VARCHAR(255) DEFAULT '';
    DECLARE i INT DEFAULT LENGTH(str);
    WHILE i > 0 DO
        SET reversed = CONCAT(SUBSTRING(str, i, 1), reversed);
        SET i = i - 1;
    END WHILE;
    RETURN reversed;
END$$

DELIMITER ;

SELECT ReverseString('Hello, World!') AS reversed_string;

+---------------------+
| reversed_string     |
+---------------------+
| !dlroW ,olleH       |
+---------------------+

DELIMITER $$

CREATE FUNCTION ReverseStringUTF8(str VARCHAR(255)) RETURNS VARCHAR(255)
BEGIN
    DECLARE reversed VARCHAR(255) DEFAULT '';
    DECLARE i INT DEFAULT LENGTH(CONVERT(str USING BINARY));
    WHILE i > 0 DO
        SET reversed = CONCAT(SUBSTRING(CONVERT(str USING BINARY), i, 1), reversed);
        SET i = i - 1;
    END WHILE;
    RETURN CONVERT(reversed USING UTF8);
END$$

DELIMITER ;

SELECT ReverseStringUTF8('你好，世界！') AS reversed_string;

+---------------------+
| reversed_string     |
+---------------------+
| ！界世，好你       |
+---------------------+