mysql转integer排序

CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    name VARCHAR(100),
    age INT
);

INSERT INTO users (name, age) VALUES ('Alice', 25);
INSERT INTO users (name, age) VALUES ('Bob', 30);
INSERT INTO users (name, age) VALUES ('Charlie', 20);

SELECT * FROM users ORDER BY age ASC;

+----+-----------+-----+
| id | name      | age |
+----+-----------+-----+
|  3 | Charlie   |  20 |
|  1 | Alice     |  25 |
|  2 | Bob       |  30 |
+----+-----------+-----+

SELECT * FROM users ORDER BY age DESC;

+----+-----------+-----+
| id | name      | age |
+----+-----------+-----+
|  2 | Bob       |  30 |
|  1 | Alice     |  25 |
|  3 | Charlie   |  20 |
+----+-----------+-----+

SELECT * FROM users ORDER BY COALESCE(age, 0) ASC;

INSERT INTO users (name, age) VALUES ('David', '35'); -- 错误示例
INSERT INTO users (name, age) VALUES ('David', 35); -- 正确示例