MySQL Count和Group By两个不同的列

Question

I have a table recommendation with fields recommender , attractionid

I want to count the how many attractionid existed in the table group by the attractionid but if there are same pairs of recommender and attractionid they are counted as 1. For example,

attractionid    recommender
      1               1
      1               2
      1               1
      2               3
      2               1
      2               2
      2               2
      2               2

expected result :

 attractionid   count
      1            2
      2            3

the rows below should be counted as 1

 attractionid    recommender
          1               1
          1               1
          2               2
          2               2
          2               2

Answer 1

Use distinct attractionid,recommender inside count function.

Query

select attractionid,
count(distinct attractionid,recommender) as `count`
from recommendation
group by attractionid;

Answer 2

Try:

select attractionid, count(recommender) cnt
from (
    select distinct attractionid, recommender
    from recommendation
) x
group by attractionid