过滤加入 table

Question

我有两张桌子

Events
id - published
--------------
1  - T
2  - T
3  - F

Attributes
id - event_id - type
---------------------
1  -   1      - large
2  -   1      - large
3  -   1      - medium
4  -   2      - small
5  -   2      - small
6  -   3      - large
7  -   3      - large

我想做的是在 Events.id 和 Attributes.event_id 上加入这两个表并像这样过滤：

For all events where Events.published = True and
where Attributes.type != large or medium
get the percentage of those events which fit the filters / all events

output of sql query
event_type                    - totals - event_ids - percentage
-----------------------------------------
"events that fit filter"      - 2      - [1,2]     - 66.66% -- (2/3)
"events that dont fit filter" - 1      - [3]       - 33.33% -- (1/3)

Answer 1

For all events where Events.published = True and where Attributes.type != large or medium get the percentage of those events which fit the filters / all events

select avg( e.published and a.type not in ('large', 'medium') )
from events e join
     attributes a
     on e.id = a.event_id;

这使用了这样一个事实，即 MySQL 将布尔值视为 1 表示真，0 表示假。

编辑：

哦，你想要这个每个事件。为此，使用两个聚合级别：

select avg(flag)
from (select e.id, 
             max( e.published and a.type not in ('large', 'medium') ) as flag
      from events e join
           attributes a
           on e.id = a.event_id
      group by e.id
     ) e;

Answer 2

select 
    case when e.published and a.type not in('large','medium') then 'Met condition' else 'Not met condition' end conditions
    , count(distinct e.id) totals
    , group_concat(distinct e.id) event_ids
    , count(distinct e.id) * 100.0 / x.total_cnt percentage
from events e
join Attributes a on a.event_id = e.id
cross join (select count(*) as total_cnt from events) x
group by case when e.published and a.type not in('large','medium') then 'Met condition' else 'Not met condition' end, total_cnt

db<>fiddle here

过滤加入 table

Filtering a joined table

mysql

sql

metabase