最近有蛮多小伙伴在跳槽找工作，但对于年限稍短的软件测试工程师，难免会需要进行笔试，而在笔试中，基本都会碰到一道关于数据库的大题，今天这篇文章呢，就收录了下最近学员反馈上来的一些数据库笔试题，包含答案！
1、依据以下学生表、班级表，按要求写 SQL
答案：
1、
select * from student a
left join class b on a.c_id = b.id
where score = (
select max(score) from student)
2、
select b.name,count(*),avg(score) as avgScore from student a,class b
where a.c_id = b.id
group by b.name
order by avgScore;
2、Table A 保存客户的基本信息；Table B 保存客户的资产负债信息。按要求写 SQL
答案：
（1）select ID from A where name = '李四';
（2）select NO,NAME，ID from A,B where A.NO = B.NO AND DEPOSIT >= 1000;
（3）select COUNTRY,count(*) FROM A GROUP BY COUNTRY;
（4）SELECT '80 后' as 年龄段，sum(CREDIT) AS '信用卡余额' FROM A,B WHERE A.NO = B.NO AND BIRTH >= 19800101 AND BIRTH < 19900101
UNION
SELECT '90 后' as 年龄段，sum(CREDIT) AS '信用卡余额' FROM A,B WHERE A.NO = B.NO AND BIRTH >= 19900101 AND BIRTH < 20000101;
3、数据库(编写示例 sql)
答案：
select orderNo, if(status=1,'新建','处理中') from OrderTrans;
select DATE_FORMAT(a.crttime,'%m-%d-%Y') ,username,count(*) from testCase a,User b where a.crtUser = b.UserId group by DATE_FORMAT(a.crttime,'%m-%d-%Y'),b.username, having status = '成功';
select count(*),sum(amount),DATE_FORMAT(crttime,'%m-%d-%Y') from OrderInfo group by
DATE_FORMAT(crttime,'%m-%d-%Y')；
4、现有三张数据表如下：学生资料表：记录学生基本信息；课程表：记录课程基本信息；成绩表：记录每人各门课程成绩的信息，1 个学生对应多个成绩，1 个成绩只属于一个学生，一个课程
答案：
Select * from students where jg = ‘湖北’ and birthday = ‘1992-6-1’ order by no asc;
Select avg(so.cj),min(so.cj),max(so.cj),sum(so.cj) from student st,course c,source so where st.no = so.no and c.kebh=so.kebh and st.name = ‘王华’ group by st.no;
Select st.no,st.name,st.bj,c.kebh,c.kcmc,so.cj from student st,course c,source so where st.no = so.no and c.kebh=so.kebh and st.name = ‘张三’ order by so.cj desc;
5、有三张表 Contacts 库 Consultant 表、Basket 库 BaseOrder 表、Basket 库 OrderDetails 表，按要求写 SQL
答案：
Select Consultant.SubsidiaryID, BaseOrder.* from Consultant, BaseOrder where Consultant.ConsultantID = BaseOrder.ConsultantID and Consultant.SubsidiaryID = 29 order by Orderid desc;
Select BaseOrder.ConsultantID,sum(OrderDetails.TotalPrice) from BaseOrder,OrderDetails where BaseOrder.Orderid=OrderDetails.Orderid and month(OrderDate) = 5 group by BaseOrder.ConsultantID;
Insert into Consultant (ConsultantID,ConstultantStatusID,SubsidiaryID,Name) values (200000,10,29,’Gary’);
Delete from Consultant where Name like ‘%Gary%’;
Update BaseOrder set OrderDate = sysdate() where ConsultantID in (select ConsultantID from BaseOrder where ConsultantID=100003 order by OrderDate desc limit 0,1);
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