delete与select

多表连接实现删除：

delete from sc

from sc join student on sc.sno = student.sno

where grade <60 and sdept = '计算机系'

此处中的delete操作不可写成与select操作一样

select * from sc,student                                    正确

where sc.sno=student.sno and grade <60 and sdept='计算机系'

而

delete from sc, student                                     错误

 where sc.sno = student.sno and grade <60 and sdept = '计算机系'