MySQL 8.0

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CREATE TABLE `table1` (
 `class_id` int(11) NOT NULL AUTO_INCREMENT,
 `student` longtext NOT NULL,
 PRIMARY KEY (`class_id`)
) ENGINE=InnoDB   DEFAULT CHARSET=latin1;

INSERT INTO `table1`(`student`) VALUES ('["A","B"]'), ('["G","K","E"]'), ('["A","B","I"]');

Records: 3  Duplicates: 0  Warnings: 0


SELECT * FROM table1


class_id
student


1
["A","B"]

2
["G","K","E"]

3
["A","B","I"]


SELECT DISTINCT(class_id), student
FROM
    table1,
    JSON_TABLE(
        student,
        "$[*]" COLUMNS(
    VALUE TEXT
        PATH "$"
    )
    ) DATA
WHERE DATA
    .Value IN("A", "B", "C", "D", "E", "F", "G")


class_id
student


1
["A","B"]

2
["G","K","E"]

3
["A","B","I"]