sql - 如何使用 Where 条件从一个表中检索同一列两次

Question

我试图从一个表中检索一列两次，例如：

select M.Event_Name as 'Male',
       F.Event_Name as 'Female' 
from   Table1 M, Table1 F
where  M.Gender = 'M'
       and F.Gender = 'F'
       and F.Country = 12
       and M.Country = 12

表1数据

ID    Event_Name   Gender  Country
1     Cricket      M       12
2     FootBall     M       13
3     BasketBall   M       12
4     Hockey       M       12
5     Tennis       M       13
6     Volly Ball   M       13
7     Cricket      F       13
8     FootBall     F       13
9     BasketBall   F       12
10    Hockey       F       13
11    Tennis       F       12
12    Volly Ball   F       12

我得到的是：

Male           Female
Cricket        Tennis
Cricket        BasketBall
Cricket        Volly ball
BasketBall     Tennis
BasketBall     BasketBall
BasketBall     Volly ball
Hockey         Tennis
Hockey         BasketBall
Hockey         Volly ball

期待：

Male          Female
Cricket       Tennis
BasketBall    BasketBall
Hockey        Volly ball

帮帮我。。谢谢

Answer 1

您应该能够使用这样的东西，其中包含PIVOT：

select M as Male, 
  F as Female
from
(
  select event_name, gender,
    row_number() over(partition by gender, country order by id) rn
  from yourtable
  where gender in ('M', 'F')
    and country = 12
) src
pivot
(
  max(event_name)
  for gender in (M, F)
) piv

请参阅带有演示的 SQL Fiddle

或者您可以使用带有CASE语句的聚合函数：

select 
  max(case when gender = 'M' then event_name end) male,
  max(case when gender = 'F' then event_name end) female
from
(
  select event_name, gender,
      row_number() over(partition by gender, country order by id) rn
  from yourtable 
  where gender in ('M', 'F')
    and country = 12
) src
group by rn

请参阅带有演示的 SQL Fiddle

两者都产生相同的结果：

|       MALE |     FEMALE |
---------------------------
|    Cricket | BasketBall |
| BasketBall |     Tennis |
|     Hockey | Volly Ball |