根据教材中的用户表,并完成以下sql查询
1. select *from user where name like '李%';
2. select * from user where city='北京';
3. update user set credit='240' where name='郭玉';
4. update user set ename=null where name='郭玉';
5. update user set credit=credit-1;
6. delete from user;
7. delete from user where credit<300;