ALTER TABLE pm_user
    ADD COLUMN password_count INT NOT NULL DEFAULT 0 COMMENT '密码修改次数' AFTER password;

ALTER TABLE pm_exam_student
    ADD COLUMN exam_unit VARCHAR(255) NULL COMMENT '服务单元' AFTER exam_room;

ALTER TABLE pm_exam_student
    ADD COLUMN course_name VARCHAR(255) NOT NULL COMMENT '课程名称' AFTER course_code;
