使用多列

Question

我有一个我想查询的Sqlite数据库。我的基本SQL知识使我能够查询我需要的大部分内容但是我被困在这里：

该表看起来像这样（简化！）：

| Name            | Year | Title   | Musician 1 | Musician 2  |
| --------------- | ---- | ------- | ---------- | ----------- |
| Doe, Jon        | 2007 | Title 1 | Beatles    | The Stooges |
| May, Peter      | 2001 | Title 2 |            | Beatles     |
| Schmidt, Andrea | 1997 | Title 3 | Nick Cave  |             |

我希望能够查询Top Musician in the 2000s并获得类似

的输出

| Name        | Count |
| ----------- | ----- |
| Beatles     | 2     |
| The Stooges | 1     |

你怎么会这样做？谢谢！

Answer 1

如果我理解正确，你需要这个

select  count(*), name from (
    select Musician_1 as Name from table where Year >= 2000
    union all 
    select Musician_2 as Name from table where Year >= 2000
) t
group by Name 
order by count(*) desc

Answer 2

你可以使用联盟全部

  select musician, count(*) from (

      select year, musician_1 as musician
      from my_table 
      union  all

      select year, musician_2
      from my_table 
  ) t 
  where t.year between 2000 and 2010
  group by t.musician