Question

Company_ID  Priority
1               1
1              10
1               1
1              10
2               1
3               1
3               1
4               1
8               1

我的数据库中有上表（类似），我需要计算优先级= 1的公司ID的发生频率。

即。预期结果，

Frequency   NoOfCompanies
1               3
2               2

3家公司优先1次记录3次。 2家公司优先1次记录2次。

我有我试过的查询，并不想与我拥有的所有联接混淆。以上是简化版本，因此易于理解。

Answer 1

您需要将数据汇总两次：

SELECT Frequency, COUNT(*) NoOfCompanies
FROM (
  SELECT COUNT(*) Frequency
  FROM Companies
  WHERE Priority = 1
  GROUP BY Company_ID
) Frequencies
GROUP BY Frequency
ORDER BY Frequency

SQLFiddle here

Answer 2

让我们制作一些测试数据：

DECLARE @MyTable TABLE
(
    Company_ID  int,
    Priority    int
)

INSERT INTO @MyTable
( Company_ID, Priority )
VALUES
(1, 1),
(1, 10),
(1, 1),
(1, 10),
(2, 1),
(3, 1),
(3, 1),
(4, 1),
(8, 1);

现在让我们看看每家公司的频率：

SELECT Company_ID, Priority, COUNT(*) AS Frequency FROM @MyTable
GROUP BY Company_ID, Priority

输出：

Company_ID  Priority    Frequency
1   1   2
2   1   1
3   1   2
4   1   1
8   1   1
1   10  2

现在让我们看看每个频率的计数：

SELECT Frequency, COUNT(d.Company_ID) NoOfCompanies FROM
(
SELECT Company_ID, Priority, COUNT(*) AS Frequency FROM @MyTable
GROUP BY Company_ID, Priority
) d
GROUP BY Frequency

输出：

Frequency   NoOfCompanies
1   3
2   3

Answer 3

这应该在DB2中执行：

使用topPriority AS（SELECT Company_ID FROM table WHERE priority = 1）

SELECT Company_ID，COUNT（*）FROM topPriority GROUP BY Company_ID

编辑：有人更快......

计算发生的频率

3 个答案: