Oracle SQL，如果值对不同情况成立，则分配名称

Question

我遇到了无法解决的问题。

with t as (
select 'Apple' a, 2016 yr from dual
union all select 'Tesla' a, 2016 yr from dual
union all select 'Microsoft' a, 2016 yr from dual
union all select 'Google' a, 2016 yr from dual
union all select 'Apple' a, 2017 yr from dual
union all select 'Google' a, 2017 yr from dual
union all select 'Apple' a, 2018 yr from dual
union all select 'Amazon' a, 2018 yr from dual
union all select 'Tesla' a, 2018 yr from dual
union all select 'Nvdia' a, 2018 yr from dual
)

select * from t;

如果数据在所有 3 年的“a”列中都存在，我想分配一个值“好” 如果数据在“a”列中存在 2 年任意组合（2016 年、2017 年）或（2017 年、2018 年）或（2016 年、2018 年），则分配值“平均” 如果数据在“a”列中仅存在 1 年（2016 年）或（2017 年）或（2018 年），则分配值“坏”

期望的输出：

我试过(Case)方法，好像不行。

这里的 SQL FIDDLE UK https://dbfiddle.uk/?rdbms=oracle_18&fiddle=7eda42b2658ee571f7a2e66fd57c0c09

Answer 1

count 的解析形式可能会有所帮助。

SQL> with t as (
  2  select 'Apple' a, 2016 yr from dual
  3  union all select 'Tesla' a, 2016 yr from dual
  4  union all select 'Microsoft' a, 2016 yr from dual
  5  union all select 'Google' a, 2016 yr from dual
  6  union all select 'Apple' a, 2017 yr from dual
  7  union all select 'Google' a, 2017 yr from dual
  8  union all select 'Apple' a, 2018 yr from dual
  9  union all select 'Amazon' a, 2018 yr from dual
 10  union all select 'Tesla' a, 2018 yr from dual
 11  union all select 'Nvdia' a, 2018 yr from dual
 12  )
 13  select a, yr,
 14    case when count(*) over (partition by a) = 3 then 'good'
 15         when count(*) over (partition by a) = 2 then 'average'
 16         when count(*) over (partition by a) = 1 then 'bad'
 17    end res
 18  From t
 19  order by yr, a;

A                 YR RES
--------- ---------- -------
Apple           2016 good
Google          2016 average
Microsoft       2016 bad
Tesla           2016 average
Apple           2017 good
Google          2017 average
Amazon          2018 bad
Apple           2018 good
Nvdia           2018 bad
Tesla           2018 average

10 rows selected.

SQL>