获取 x 行数，其中 id = id(other table) 具有该 id 的行数最多

Question

x = 无所谓

table一个

0 row0
1 row1
2 row2

table B

0 x
1 x
0 X
2 X
2 X
0 x

在此示例中有 3 行 0、2 行 2 和 1 行 1。

我想得到例如行数最多的两行。

期望的结果：

0 row0 ==> because 3 rows in b is the highest amount.
2 row2 ==> because 2 rows in b is the second highest amount.

我目前的尝试：

SELECT Id, Name FROM A
WHERE Id =
(
SELECT IdB FROM B
GROUP BY IdB 
ORDER BY count(IdB) DESC
LIMIT 2
)

编辑：我使用 mysql

谢谢

Answer 1

不确定您想如何处理关系。

这样做是根据您的 ID 将两个 table 连接 (learn more about joins) 在一起，然后汇总计算 B.IDB 出现次数的结果，并显示该计数以及来自 table A

的名字

SELECT A.Name, count(B.IDB) cnt
FROM A
INNER JOIN IDB
 on A.ID = B.IDB
GROUP BY A.Name
ORDER BY count(B.IDB) desc
LIMIT 2

但是对于你的例子，这应该 return

Name cnt
row0 3
row2 2

Answer 2

您想 JOIN 通过 id:

将您的桌子放在一起

SELECT
  A.id,
  A.name
FROM
  A join
  B on A.id = B.id
GROUP BY
  A.name
ORDER BY
  count(B.id) desc
LIMIT 2

SQLFIDDLE

这将 return 输出与上面的示例相匹配。

Answer 3

-- 样本table

-- table 架构

create table A (id int, name varchar(10))

 insert into A 
 values (0, 'row0')
  insert into A 
 values (1, 'row1')
 insert into A 
 values (2, 'row2')

 select * from A

-- table 架构

 create table B (id int, name varchar(10))

 insert into B 
 values (0, 'X')
 insert into B 
 values (0, 'X')
 insert into B 
 values (0, 'X')
 insert into B 
 values (0, 'X')
   insert into B 
 values (1, 'X')
 insert into B 
 values (2, 'X')
 insert into B 
 values (2, 'X')
 insert into B 
 values (2, 'X')
 insert into B 
 values (2, 'X')
 insert into B 
 values (2, 'X')
 insert into B 
 values (2, 'X')

 select * from B

--查询

 select Top 2 A.name, count(B.id) from A
  inner join B on A.id = b.id
   group by A.name
 order by  count(A.name) desc

Answer 4

你可以试试;

select a.name, b.count
  from A a,
       (select idB, count(idB) count from B group by idB) b
 where a.id = b.idB
   and count > 1

获取 x 行数，其中 id = id(other table) 具有该 id 的行数最多

Getting x amount of rows where id = id(other table) with the highest amount of rows with that id

mysql

sql

greatest-n-per-group