我的组按类型和计数自我加入表以获取摘要

Question

Here is my sql

select count(type), type
from tasks
group by type

Here having 4 rows.

count(type) type
8           Trial
7           New
3           Service
4           Uninstall

How do I get in one row result in return

Trial   New Service Uninstall
8       7   3       4

I know it has to self-joining the table. But I am not able to get exactly.

Here is the sample table data

id  type        date
1   New         2017-10-07
2   Trial       2017-10-01
3   New         2017-10-02
4   Uninstall   2017-10-05
5   Trial       2017-10-06
6   Trial       2017-10-07

Answer 1

SELECT MAX(CASE WHEN type = 'Trial' THEN count_type END) as Trial,
       MAX(CASE WHEN type = 'New' THEN count_type END) as New,
       MAX(CASE WHEN type = 'Service' THEN count_type END) as Service,
       MAX(CASE WHEN type = 'Uninstall' THEN count_type END) as Uninstall
FROM (select count(type) as count_type , type
      from tasks
      group by type) T

Answer 2

This is done with conditional aggregation:

select
  sum(type = 'Trial') as trial,
  sum(type = 'New') as new,
  sum(type = 'Service') as service,
  sum(type = 'Uninstall') as uninstall
from mytable;

true is 1 and false is 0 in MySQL, so we can use SUM , to count matches.