一個SQL查詢，而不是許多

Question

假設我有一個MySQL表只有兩列：

id 
invited_by_id 

，我想知道 有多少次出現在invited_by_id列每個ID。

如何使這隻使用一個查詢？

Answer 1

一個簡單的invited_by_id列GROUP BY是你所需要的，因爲它擁有相同的ID值作爲id柱：

SELECT invited_by_id, COUNT(*) AS invited_count FROM table GROUP BY invited_by_id 

Answer 2

select id1.id, (count*) 
from id as id1 
inner join id as id2 on id1.id = id2.invited_by_id 
group by id1.id 

Answer 3

select invited_by_id, count(*) from table group by invited_by_id 

Answer 4

SELECT m.id 
    , grp.cnt 
FROM 
    (SELECT DISTINCT id 
     FROM mytable 
    ) AS m 
    LEFT JOIN 
     (SELECT invited_by_id 
      , COUNT(*) AS cnt 
     FROM mytable 
     GROUP BY invited_by_id 
    ) AS grp 
    ON grp.invited_by_id = m.id