笔试题1：
1、select * from tablex where name = "张*" order by age 默认升序
select * from tablex where name contains ”张“ order by age desc 降序
2 select name from tablex ，tabley where tablex.code=tabley.code
and class="计算机" and score<60；
3 select name ，class，score from tablex ，tabley where tablex.code=tabley.code
select name ，class，score from tablex inner join tabley on tablex.code=tabley.code
4 select name ，class，score from tablex lift join tabley on tablex.code=tabley.code
5 insert into tablex(code,name,age)values("97005","赵六"，“20”)
6 update tablex set age =21 where code =97004
7 delete * from tablex where code not in (select code form tabley where score is null ) # not in 语句容易出bug