写一个方法求集合的比值，请大家帮忙！！！

Question

现在有两组数据集合list<DataEntity>
public class DataEntity{
   private Long id;
   private String name;
   private Double value;
   private Date date;
   .....
}
一组为：
+----+----------+-------+------------+
| id | name     | value1| date       |
+----+----------+-------+------------+
|  1 | 北京大厦 |    12 | 2009-09-01 |
|  2 | 北京大厦 |    10 | 2009-09-02 |
|  3 | 北京大厦 |    11 | 2009-09-03 |
|  4 | 北京大厦 |    14 | 2009-09-04 |
| 13 | 南京大厦 |    14 | 2009-09-01 |
| 14 | 南京大厦 |    16 | 2009-09-02 |
| 15 | 南京大厦 |    18 | 2009-09-03 |
| 16 | 南京大厦 |    10 | 2009-09-04 |另一组为：
+----+----------+-------+------------+
| id | name     | value2| date       |
+----+----------+-------+------------+
|  1 | 北京大厦 |    13 | 2009-09-01 |
|  2 | 北京大厦 |    12 | 2009-09-02 |
|  3 | 北京大厦 |    14 | 2009-09-03 |
|  4 | 北京大厦 |    11 | 2009-09-04 |
| 13 | 南京大厦 |    14 | 2009-09-01 |
| 14 | 南京大厦 |    15 | 2009-09-02 |
| 15 | 南京大厦 |    17 | 2009-09-03 |
| 16 | 南京大厦 |    10 | 2009-09-04 |写一个方法按照时间对应关系得到
+----+----------+-------+------------+
| id | name  |value1/value2| date    |
+----+----------+-------+------------+
|  1 | 北京大厦 | 12/13 | 2009-09-01 |
|  2 | 北京大厦 | 10/11 | 2009-09-02 |
|  3 | 北京大厦 | 11/14 | 2009-09-03 |
|  4 | 北京大厦 | 14/11 | 2009-09-04 |
| 13 | 南京大厦 | 14/14 | 2009-09-01 |
| 14 | 南京大厦 | 16/15 | 2009-09-02 |
| 15 | 南京大厦 | 18/17 | 2009-09-03 |
| 16 | 南京大厦 | 10/10 | 2009-09-04 |急用，请大家多帮忙，非常感谢！！！

Answer 1

select t1.name,t1.value1+'/'+t2.value2 as 'value1/value2' ,t1.date from 
table1 t1,table2 t2 where t1.name=t2.name and t1.date=t2.date

Answer 2

我是从一个表中查询数据，每天9：00-17：00上班时间的用能量/全天的用能量。如果接近1的话说明能源没有浪费，比值越小说明下班时间浪费严重。谢谢回答，#2楼的SQL让我想到自连接。非常感谢！！！

Answer 3

为了试验方便，我将类型都处理成Stringpublic class DataEntity {
private long id; 
  private String name; 
  private String value; 
  private String date;
public DataEntity(long id,String name,String value,String date){
this.id=id;
this.name=name;
this.value=value;
this.date=date;
}
public long getId() {
return id;
} public String getName() {
return name;
} public String getValue() {
return value;
} public String getDate() {
return date;
}
public void setId(long id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public void setValue(String value) {
this.value = value;
}
public void setDate(String date) {
this.date = date;
}

}测试类：import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;
public class Test{
public static void main(String[] args){
List <DataEntity> listA=new ArrayList<DataEntity>();
listA.add(new DataEntity(1,"北京大厦","12","2009-09-01"));
listA.add(new DataEntity(2,"北京大厦","10","2009-09-02"));
listA.add(new DataEntity(3,"北京大厦","11","2009-09-03"));
listA.add(new DataEntity(4,"北京大厦","14","2009-09-04"));
listA.add(new DataEntity(13,"南京大厦","14","2009-09-01"));
listA.add(new DataEntity(14,"南京大厦","16","2009-09-02"));
listA.add(new DataEntity(15,"南京大厦","18","2009-09-03"));
listA.add(new DataEntity(16,"南京大厦","10","2009-09-04"));
List <DataEntity> listB=new ArrayList<DataEntity>();
listB.add(new DataEntity(1,"北京大厦","13","2009-09-01"));
listB.add(new DataEntity(2,"北京大厦","12","2009-09-02"));
listB.add(new DataEntity(3,"北京大厦","14","2009-09-03"));
listB.add(new DataEntity(4,"北京大厦","11","2009-09-04"));
listB.add(new DataEntity(13,"南京大厦","14","2009-09-01"));
listB.add(new DataEntity(14,"南京大厦","15","2009-09-02"));
listB.add(new DataEntity(15,"南京大厦","17","2009-09-03"));
listB.add(new DataEntity(16,"南京大厦","10","2009-09-04"));
Map<Long,DataEntity> map=new HashMap<Long,DataEntity>();
for(DataEntity ob:listA){
map.put(ob.getId(),ob);
}
for(DataEntity ob:listB){
if(!map.containsKey(ob.getId())){
map.put(ob.getId(),ob);
}else{
ob.setValue(map.get(ob.getId()).getValue()+"/"+ob.getValue());
map.put(ob.getId(),ob);
}
}
Set<Long> set=map.keySet();
System.out.println("id"+"  "+"name"+"   "+"value"+"   "+"date");
for(Long id: set){
System.out.println(id+"  "+map.get(id).getName()+"   "+map.get(id).getValue()+"   "+map.get(id).getDate());
}

}
}结果：
id  name   value   date
1  北京大厦   12/13   2009-09-01
2  北京大厦   10/12   2009-09-02
3  北京大厦   11/14   2009-09-03
4  北京大厦   14/11   2009-09-04
13  南京大厦   14/14   2009-09-01
14  南京大厦   16/15   2009-09-02
15  南京大厦   18/17   2009-09-03
16  南京大厦   10/10   2009-09-04