一个查询转换

题目：There are two table:

T_A (name VARCHAR2(100))

T_B (name VARCHAR2(100), name_a VARCHAR2(100));

The values are:

(1) Please write a SQL to output below result:

Name Apple Orange Banana

----------- ---------- ----------- -----------

Jane Yes Yes Yes

Leo Yes Yes No

David No No Yes

 1 select name,
 2        case when ap>=1 then 'YES' else 'NO' end ap,
 3        case when og>=1 then 'YES' else 'NO' end og,
 4        case when ba>=1 then 'YES' else 'NO' end ba
 5   from (
 6 select name, sum(ap) ap, sum(og) og, sum(ba) ba
 7   from (select name_a name,
 8                decode(b.name, 'Apple', 1, 0) ap,
 9                decode(b.name, 'Orange', 1, 0) og,
10                decode(b.name, 'Banana', 1, 0) ba
11           from t_b b)
12  group by name)

(3) Please write a SQL to output below result:

(Find rows between 2 and 4, using ROWNUM)

Name Name_a

--------- -------------

Orange Jane

Banana Jane

Apple Leo

1 select *
2   from t_b
3  where rownum < 5
4 minus
5 select * 
6   from t_b
7  where rownum  < 2

(4) Please write a Function:

This function has a parameter which has the same data type as

name in T_A and return the second fruit name in T_B.

if one person has no the second fruit, the function return the

first fruit.

Example: pass „Jane‟ as parameter, return „Orange‟; pass

„David‟, return „Banana‟.

 1 create or replace function fun1(fname in varchar2) return varchar2 is
 2 fruit varchar2(10);
 3 n varchar2(10);
 4 ap number;
 5 og number;
 6 ba number;
 7 begin
 8   select name, ap, og, ba into n,ap,og,ba
 9     from (select name, sum(ap) ap, sum(og) og, sum(ba) ba
10             from (select name_a name,
11                          decode(b.name, 'Apple', 1, 0) ap,
12                          decode(b.name, 'Orange', 1, 0) og,
13                          decode(b.name, 'Banana', 1, 0) ba
14                     from t_b b)
15            group by name) 
16    where name = fname;
17    
18    if ap = 1 and og = 1 then select 'Orange' into fruit from dual;
19    elsif ap = 1 and og = 0 and ba = 1 then select 'Banana' into fruit from dual;
20    elsif ap = 0 and og = 1 and ba = 1 then select 'Banana' into fruit from dual;
21    elsif ap = 1 and og = 0 and ba = 0 then select 'Apple' into fruit from dual;
22    elsif ap = 0 and og = 1 and ba = 0 then select 'Orange' into fruit from dual;
23    elsif ap = 0 and og = 0 and ba = 1 then select 'Banana' into fruit from dual;
24    end if;
25    
26 
27    return (fruit);
28 end fun1;

这里暂时还没想出更好的办法。。。