mysql 按逗号分割

CREATE TABLE users (
    id INT PRIMARY KEY,
    name VARCHAR(255),
    hobbies VARCHAR(255)
);

INSERT INTO users (id, name, hobbies) VALUES
(1, 'Alice', 'reading,swimming'),
(2, 'Bob', 'traveling,coding');

SELECT 
    id,
    name,
    SUBSTRING_INDEX(SUBSTRING_INDEX(hobbies, ',', n), ',', -1) AS hobby
FROM 
    users
JOIN 
    (SELECT 1 AS n UNION ALL SELECT 2 UNION ALL SELECT 3) AS numbers
ON CHAR_LENGTH(hobbies) - CHAR_LENGTH(REPLACE(hobbies, ',', '')) >= n - 1;

SELECT 
    id,
    name,
    SUBSTRING_INDEX(SUBSTRING_INDEX(hobbies, ',', n), ',', -1) AS hobby
FROM 
    users
JOIN 
    (SELECT 1 AS n UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4) AS numbers
ON CHAR_LENGTH(hobbies) - CHAR_LENGTH(REPLACE(hobbies, ',', '')) >= n - 1;

DELIMITER //

CREATE FUNCTION SPLIT_STRING(str VARCHAR(255), delim VARCHAR(12), pos INT)
RETURNS VARCHAR(255)
DETERMINISTIC
BEGIN
    DECLARE output VARCHAR(255);
    SET output = REPLACE(SUBSTRING(SUBSTRING_INDEX(str, delim, pos),
        LENGTH(SUBSTRING_INDEX(str, delim, pos - 1)) + 1),
        delim, '');
    RETURN output;
END //

DELIMITER ;

SELECT 
    id,
    name,
    SPLIT_STRING(hobbies, ',', n) AS hobby
FROM 
    users
JOIN 
    (SELECT 1 AS n UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4) AS numbers
ON CHAR_LENGTH(hobbies) - CHAR_LENGTH(REPLACE(hobbies, ',', '')) >= n - 1;