SQL面试题 五（重复数据、统计）

题一:表stu

+----+------+-----+-------+

| id | sno | cno | score |

+----+------+-----+-------+

| 1 | 1001 | 1 | 89 |

| 3 | 1001 | 1 | 89 |

| 2 | 1002 | 1 | 87 |

| 4 | 1002 | 1 | 90 |

| 5 | 1003 | 1 | 86 |

+----+------+-----+-------+

1、查询出sno,cno重复的数据：

> select * from rs where (sno,cno) in (select sno,cno from rs group by sno,cno having count(*)>1);

2、查询sno,cno,score都重复的数据，且除id最小的一条数据外：

> select * from rs where (sno,cno,score) in(select sno,cno,score from rs group by sno,cno,score having count(*)>1)and
id not in (select min(id) from rs group by sno,cno,score having count(*)>1);

3、删除sno,cno,score都重复的数据，保留id最小的一条数据：
>（SQL Server未验证）delete from rs where (sno,cno,score) in(select sno,cno,score from rs group by sno,cno,score having count(*)>1)and id not in (select
min(id) from rs group by sno,cno,score having count(*)>1);

>（MySQL）

create table temp as select * from rs where (sno,cno,score) in(select sno,cno,score from rs group by sno,cno,score
having count(*)>1)and id not in (select min(id) from rs group by sno,cno,score having count(*)>1);

delete from rs where id in(select id from temp);

drop table temp;

题二:有以下三张表

商品表：tp

+-------+-------+

| pcode | pname |

+-------+-------+

| 1 | cpu |

| 2 | 内存 |

| 3 | 硬盘 |

城市表：tc

+-----+-------+

| cno | cname |

+-----+-------+

| 101 | 广州 |

| 102 | 深圳 |

| 103 | 上海 |

+-----+-------+

销售表：ts

+-------+-----+-------+

| pcode | cno | count |

+-------+-----+-------+

| 1 | 101 | 10000 |

| 1 | 102 | 500 |

| 1 | 103 | 20000 |

| 2 | 101 | 40000 |

| 2 | 103 | 30000 |

| 3 | 102 | 90000 |

+-------+-----+-------+

问题：需要得到以下结构的统计结果，写出SQL语句：

广州 深圳 上海 总计

CPU 10000 5000 20000 35000

内存 40000 0 30000 70000

硬盘 0 90000 0 90000

总计 50000 95000 50000 195000

>