Example:
First, create a new table and insert values:

DROP TABLE IF EXISTS table_score_one;

CREATE TABLE table_score_one (
    id INT (10) NOT NULL PRIMARY KEY auto_increment,
    student_no VARCHAR (10) NOT NULL,
    student_name VARCHAR (10) NOT NULL,
    class_no VARCHAR (10) NOT NULL,
    class_name VARCHAR (10) NOT NULL,
    score INT (10) NOT NULL
) DEFAULT CHARSET='utf8';
INSERT INTO `table_score_one` VALUES ('1', '201601', 'Zhang San', '0001', 'Mathematics', '98');
INSERT INTO `table_score_one` VALUES ('2', '201601', 'Zhang San', '0002', 'Chinese', '66');
INSERT INTO `table_score_one` VALUES ('3', '201602', 'Li Si', '0001', 'Mathematics', '60');
INSERT INTO `table_score_one` VALUES ('4', '201602', 'Li Si', '0003', 'English?', '78');
INSERT INTO `table_score_one` VALUES ('5', '201603', 'Wang Wu', '0001', 'Mathematics', '99');
INSERT INTO `table_score_one` VALUES ('6', '201603', 'Wang Wu', '0002', 'Chinese', '99');
INSERT INTO `table_score_one` VALUES ('7', '201603', 'Wang Wu', '0003', 'English?', '98');

Where auto_increment represents the sequential generation of values. The default starts from 1.
The table is as follows:

The second step updates the value:

update table_score_one set class_name ='Mathematics' , class_no = '0001' where id = 6;

As shown in the picture:

The third step:
Delete all the same data except the id.

delete table_test_one where id not in (select min(id) from table_test_one group by student_no, student_name, class_no, class_name, score);

The above statement means: first, by grouping according to student_no, student_name, class_no, class_name and score, we can find the smallest id of each group, and then delete the id that is not in the result of the query.
But there will be a mistake:

DELETE
FROM
    table_score_one
WHERE
    id NOT IN (
        SELECT
            a.min_id
        FROM
            (
                SELECT
                    min(id) AS min_id
                FROM
                    table_score_one
                GROUP BY
                    student_no,
                    class_no,
                    class_name,
                    score
            ) a
    );

Aliases should be established for the results.
Reference resources: http://blog.csdn.net/u013142781/article/details/50836476