如何使用MySQL一个表中的字段更新另一个表中字段

update student s, city cset s.city_name = c.namewhere s.city_code = c.code;

update a, bset a.title=b.title, a.name=b.namewhere a.id=b.id

update student s set city_name = (select name from city where code = s.city_code);

UPDATE "SYS_ROLE" ASET A ."DEPT_ID" = (  SELECT    c."id"  FROM    "his_department_info" c  WHERE    c."dept_name" = A ."ROLE_NAME"