mysql - SQL查询根据计数和一些过滤器查找最大值

Question

表格如下所示:

/* Create a table called test */
CREATE TABLE test(Id integer PRIMARY KEY,Col_Key text, Ng text, node text);

/* Create few records in this table */
INSERT INTO test VALUES(1,'key1','g1','n2');
INSERT INTO test VALUES(2,'key1','g2','n3');
INSERT INTO test VALUES(3,'key2','g3','n1');
INSERT INTO test VALUES(4,'key2','g4','n1');
INSERT INTO test VALUES(5,'key3','g5','n1');
INSERT INTO test VALUES(6,'key3','g6','n2');
INSERT INTO test VALUES(7,'key4','g7','n1');
INSERT INTO test VALUES(8,'key4','g8','n1');
INSERT INTO test VALUES(9,'key5','g8','n4');
INSERT INTO test VALUES(10,'key5','g9','n4');
INSERT INTO test VALUES(11,'key6','g10','n4');
INSERT INTO test VALUES(12,'key6','g11','n4');
INSERT INTO test VALUES(13,'key7','g11','n4');
INSERT INTO test VALUES(14,'key9','q11','n3');
INSERT INTO test VALUES(15,'key9','q11','n2');
INSERT INTO test VALUES(16,'key10','q12','n1');
COMMIT;

我正在尝试从具有最大计数且 Ng 值以 g 开头的节点列中获取值。

我做过这样的事情:

SELECT TEMP.node,COUNT(TEMP.node) FROM (SELECT Col_Key,Ng,node 
from test WHERE (Ng LIKE 'g%')) TEMP GROUP BY TEMP.node;

结果如下:

但是，在结果中我只想要 n4 和 n1 结果(只有节点列不计)，因为它们具有最大计数。我无法在我的查询中添加这部分。请帮忙。

以上数据只是一小部分数据，但我的 SQL 表中将有数千行，因此我的查询应该是高效的。

PS :- 我试过在下面做 :

SELECT TEMP2.node,TEMP2.CNT FROM (SELECT TEMP.node,COUNT(TEMP.node) AS CNT FROM (SELECT Col_Key,Ng,node 
from test WHERE (Ng LIKE 'g%')) TEMP GROUP BY TEMP.node) TEMP2 WHERE TEMP2.CNT = (SELECT MAX(TEMP2.CNT) FROM TEMP2);

但是带有 where 子句的查询的最后一部分是错误的，因为它无法找到表 TEMP2。

但是这个 WHERE 子句可以让我知道我想要什么。

结果应该是:

node 
n1
n4

Answer 1

怎么样:

SELECT
  t.node,
  COUNT(*)
FROM
  test t
WHERE
  t.Ng like 'g%'
GROUP BY
  t.node
HAVING
  COUNT(*) = (
    SELECT 
      MAX(a.count_of_nodes)
    FROM
    (
      SELECT
        node,
        COUNT(*) AS count_of_nodes
      FROM
        test
      WHERE
        Ng like 'g%'
      GROUP BY
        node
    ) a
  )
;

祝你好运!