MariaDB 10.6

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select version();

version()

10.6.9-MariaDB-1:10.6.9+maria~deb11

create table Student(city varchar(10));
-- your error:
ALTER TABLE Student MODIFY(city varchar(20));

You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '(city varchar(20))' at line 2

ALTER TABLE Student MODIFY city varchar(20) ;

Records: 0  Duplicates: 0  Warnings: 0

SHOW CREATE TABLE Student;

Table
Create Table

Student
CREATE TABLE `Student` (
  `city` varchar(20) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4