一个SQL查询而不是很多

Question

假设我有一个只有2列的MySQL表：

id
invited_by_id

我想知道 每个ID在invited_by_id列中显示的次数。

如何仅使用一个查询进行此操作？

Answer 1

GROUP BY列上的简单invited_by_id就是您所需要的，因为它与id列保持相同的ID值：

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