sql连表删除:http://www.lanxinbase.com/?tag=sql%E8%BF%9E%E8%A1%A8%E5%88%A0%E9%99%A4
sql实现两表关联更新:https://blog.csdn.net/qq_43429919/article/details/124036257
Update student Set Sage=22 Where Sno=’201215121’;
UPDATE (要更新的表) table1 t1 SET t1.字段1 = t2.字段1, t1.字段2 = t2.字段2, FROM (数据来源表) table2 t2 WHERE t1.key = t2.key
UPDATE (要更新的表) table1 t1, table2 t2 SET t1.字段1 = t2.字段1, t1.字段2 = t2.字段2, WHERE t1.key = t2.key
Delete From SC Where Son in( Selete Sno From Student Where Sdept=’CS’);
delete FROM `t1` using `t1` left join `t2` on t1.id= t2.id where 1 and t2.id is null;