Question

person_id | manager_id | name |
          |            |      |
-------------------------------

查询以查找监督最大员工人数的经理姓名？

已添加：这是唯一的表格。是的自我引用。 DB是mysql。递归查询也可以。

Answer 1

此查询返回经理的manager_id和manager_name以及最大雇员人数。

诀窍在HAVING子句中，它允许聚合并计算多行。

SELECT manager_id,name, count(*) 
    FROM table 
    GROUP BY manager_id, name
    HAVING max(count(*));

您可以阅读更多内容，但内容丰富w3schools.com HAVING clause tutorial。

如果manager_id引用同一个表中的人员ID Svinto's answer might be more suitable。

Answer 2

SELECT name 
FROM table 
WHERE person_id = (
    SELECT manager_id 
    FROM table 
    GROUP BY manager_id 
    HAVING max(count(*)))

Answer 3

我并不完全清楚你想要什么，所以如果这不是你想要的，请澄清你的问题。

如果存在平局，此查询仅返回其中一个经理：

SELECT T2.name FROM (
    SELECT manager_id
    FROM table1
    WHERE manager_id IS NOT NULL
    GROUP BY manager_id
    ORDER BY count(*) DESC
    LIMIT 1
) AS T1
JOIN table1 AS T2
ON T1.manager_id = T2.person_id

查询结果：

Bar

这是一个查询，在存在平局的情况下，获取具有绑定最大计数的所有经理：

SELECT name FROM (
    SELECT manager_id, COUNT(*) AS C
    FROM person
    WHERE manager_id IS NOT NULL
    GROUP BY manager_id) AS Counts
JOIN (
    SELECT COUNT(*) AS C
    FROM person
    WHERE manager_id IS NOT NULL
    GROUP BY manager_id
    ORDER BY COUNT(*) DESC
    LIMIT 1
) AS MaxCount
ON Counts.C = MaxCount.C
JOIN person
ON Counts.manager_id = person.person_id

第二个查询的结果：

Foo
Bar

这是我的测试数据：

CREATE TABLE Table1 (person_id int NOT NULL, manager_id nvarchar(100) NULL, name nvarchar(100) NOT NULL);
INSERT INTO Table1 (person_id, manager_id, name) VALUES
(1, NULL, 'Foo'),
(2, '1', 'Bar'),
(3, '1', 'Baz'),
(4, '2', 'Qux'),
(5, '2', 'Quux'),
(6, '3', 'Corge');

Answer 4

假设manager_id引用了person_id和table的名称：table_name

SELECT name FROM (
  SELECT manager_id
  FROM table_name
  GROUP BY manager_id
  ORDER BY COUNT(*) DESC
  LIMIT 1
) t
INNER JOIN table_name ON t.manager_id = table_name.person_id

修改删除了HAVING MAX COUNT，在子查询中添加了ORDER BY COUNT DESC LIMIT 1

用于查找监督最大员工数量的经理姓名的SQL查询是什么？

4 个答案: