mysql有动态sql吗

SET @sql = CONCAT('SELECT * FROM users WHERE age > ', age);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

DELIMITER $$
CREATE PROCEDURE GetUserByAge(IN age INT)
BEGIN
    SET @sql = CONCAT('SELECT * FROM users WHERE age > ', age);
    PREPARE stmt FROM @sql;
    EXECUTE stmt;
    DEALLOCATE PREPARE stmt;
END$$
DELIMITER ;

CALL GetUserByAge(25);

PREPARE stmt FROM 'SELECT * FROM users WHERE age > ?';
SET @age = 25;
EXECUTE stmt USING @age;
DEALLOCATE PREPARE stmt;

-- 不安全的做法
SET @sql = CONCAT('SELECT * FROM users WHERE username = ', username);
PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

-- 安全的做法
PREPARE stmt FROM 'SELECT * FROM users WHERE username = ?';
SET @username = 'admin';
EXECUTE stmt USING @username;
DEALLOCATE PREPARE stmt;