UPDATE 表名 SET 列名=值，列名=值 WHERE 条件
• 更新的表不能在 set 和 where 中用于子查询;
• update 后面可以做任意的查询
更新 emp3 表中的 id 为 1 的数据，添加 address 为 BeiJing。
update emp3 e set e.address = "BeiJing" where emp_id = 1;
update emp3 e set e.address = (select address from emp3 where emp_id = 1) where e.emp_id = 2;
update emp3 e ,(select address from emp3 where emp_id = 1)t set e.address = t.address where e.emp_id =2;
update emp3 e set e.address = (select t1.address from (select emp_id, add ress from emp3)t1 where t1.emp_id = 1 ) where e.emp_id = 2;
原文：https://www.cnblogs.com/qiaoxin11/p/12796007.html