我如何计算 SQL 服务器中序列中组的最小值和最大值？

Question

我在 SQL 服务器的数据库 table 中有以下数据：

Id  Date        Val_A   Val_B   Val_C   Avg     Vector  MINMAXPOINTS
329 2016-01-15  78.09   68.40   70.29   76.50   BELOW   68.40
328 2016-01-14  79.79   75.40   76.65   76.67   BELOW   75.40
327 2016-01-13  81.15   74.59   79.00   76.44   ABOVE   81.15
326 2016-01-12  81.95   77.04   78.95   76.04   ABOVE   81.95
325 2016-01-11  82.40   73.65   81.34   75.47   ABOVE   82.40
324 2016-01-08  78.75   73.40   77.20   74.47   ABOVE   78.75
323 2016-01-07  76.40   72.29   72.95   73.74   BELOW   72.29
322 2016-01-06  81.25   77.70   78.34   73.12   ABOVE   81.25
321 2016-01-05  81.75   76.34   80.54   72.08   ABOVE   81.75
320 2016-01-04  80.95   75.15   76.29   70.86   ABOVE   80.95

列 MIMMAXPOINTS 实际上应包含 Val_B 的最低值，直到 Vector 为 'BELOW' 和 Val_A 的最高值，直到 Vector 为 'ABOVE'。因此，我们将在 MINMAXPOINTS 中具有以下值：

MINMAXPOINTS
68.40
68.40
82.40
82.40
82.40
82.40
72.29
81.75
81.75
81.75

没有光标可以吗？

任何帮助将不胜感激！

Answer 1

您可以在下面的查询中使用 case 语句，这样您就可以 select 根据每行的向量值获得一个条件值。

查询是

SELECT ID, DATE, VAL_A, VAL_B, VAL_C, AVG, VECTOR, 
CASE
    WHEN VECTOR = 'BELOW' THEN (SELECT MIN(VAL_B) FROM TABLE A)
    WHEN VECTOR = 'ABOVE' THEN (SELECT MAX(VAL_A) FROM TABLE A)
END AS MINMAXVALUE
FROM TABLE B
GO

检查是否对您有帮助。

Answer 2

修改查询以检查大于当前记录的数据组您可以使用以下使用案例陈述的查询，这将使您 select 一个基于每行向量值的条件值。

查询是

SELECT ID, DATE, VAL_A, VAL_B, VAL_C, AVG, VECTOR,
  CASE
    WHEN VECTOR = 'BELOW' THEN (SELECT MIN(VAL_B) FROM TABLE A WHERE ROWID >= B.ROWID)
    WHEN VECTOR = 'ABOVE' THEN (SELECT MAX(VAL_A) FROM TABLE A WHERE ROWID >= B.ROWID)
   END AS MINMAXVALUE

FROM TABLE B 
GO

检查这应该会产生您期望从数据中得到的结果。

Answer 3

首先应用经典gaps-and-islands来确定组（gaps/islands/above/below），然后计算每个组的MIN和MAX。

我假设 ID 列定义了行的顺序。

在 SQL Server 2008 上测试。这里是 SQL Fiddle。

示例数据

DECLARE @T TABLE
([Id] int, [dt] date, [Val_A] float, [Val_B] float, [Val_C] float, [Avg] float, 
[Vector] varchar(5));

INSERT INTO @T ([Id], [dt], [Val_A], [Val_B], [Val_C], [Avg], [Vector]) VALUES
(329, '2016-01-15', 78.09, 68.40, 70.29, 76.50, 'BELOW'),
(328, '2016-01-14', 79.79, 75.40, 76.65, 76.67, 'BELOW'),
(327, '2016-01-13', 81.15, 74.59, 79.00, 76.44, 'ABOVE'),
(326, '2016-01-12', 81.95, 77.04, 78.95, 76.04, 'ABOVE'),
(325, '2016-01-11', 82.40, 73.65, 81.34, 75.47, 'ABOVE'),
(324, '2016-01-08', 78.75, 73.40, 77.20, 74.47, 'ABOVE'),
(323, '2016-01-07', 76.40, 72.29, 72.95, 73.74, 'BELOW'),
(322, '2016-01-06', 81.25, 77.70, 78.34, 73.12, 'ABOVE'),
(321, '2016-01-05', 81.75, 76.34, 80.54, 72.08, 'ABOVE'),
(320, '2016-01-04', 80.95, 75.15, 76.29, 70.86, 'ABOVE');

查询

为了更好地理解它是如何工作的，检查每个 CTE 的结果。

CTE_RowNumbers计算两个行号序列。

CTE_Groups 为每个组分配一个编号 (above/below)。

CTE_MinMax 为每个组计算 MIN/MAX。

最终 SELECT 选择 MIN 或 MAX 到 return。

WITH
CTE_RowNumbers
AS
(
    SELECT [Id], [dt], [Val_A], [Val_B], [Val_C], [Avg], [Vector]
        ,ROW_NUMBER() OVER (ORDER BY ID DESC) AS rn1
        ,ROW_NUMBER() OVER (PARTITION BY Vector ORDER BY ID DESC) AS rn2
    FROM @T
)
,CTE_Groups
AS
(
    SELECT [Id], [dt], [Val_A], [Val_B], [Val_C], [Avg], [Vector]
        ,rn1-rn2 AS Groups
    FROM CTE_RowNumbers
)
,CTE_MinMax
AS
(
    SELECT [Id], [dt], [Val_A], [Val_B], [Val_C], [Avg], [Vector]
        ,MAX(Val_A) OVER(PARTITION BY Groups) AS MaxA
        ,MIN(Val_B) OVER(PARTITION BY Groups) AS MinB
    FROM CTE_Groups
)
SELECT [Id], [dt], [Val_A], [Val_B], [Val_C], [Avg], [Vector]
    ,CASE 
        WHEN [Vector] = 'BELOW' THEN MinB
        WHEN [Vector] = 'ABOVE' THEN MaxA
    END AS MINMAXPOINTS
FROM CTE_MinMax
ORDER BY ID DESC;

结果

+-----+------------+-------+-------+-------+-------+--------+--------------+
| Id  |     dt     | Val_A | Val_B | Val_C |  Avg  | Vector | MINMAXPOINTS |
+-----+------------+-------+-------+-------+-------+--------+--------------+
| 329 | 2016-01-15 | 78.09 | 68.4  | 70.29 | 76.5  | BELOW  | 68.4         |
| 328 | 2016-01-14 | 79.79 | 75.4  | 76.65 | 76.67 | BELOW  | 68.4         |
| 327 | 2016-01-13 | 81.15 | 74.59 | 79    | 76.44 | ABOVE  | 82.4         |
| 326 | 2016-01-12 | 81.95 | 77.04 | 78.95 | 76.04 | ABOVE  | 82.4         |
| 325 | 2016-01-11 | 82.4  | 73.65 | 81.34 | 75.47 | ABOVE  | 82.4         |
| 324 | 2016-01-08 | 78.75 | 73.4  | 77.2  | 74.47 | ABOVE  | 82.4         |
| 323 | 2016-01-07 | 76.4  | 72.29 | 72.95 | 73.74 | BELOW  | 72.29        |
| 322 | 2016-01-06 | 81.25 | 77.7  | 78.34 | 73.12 | ABOVE  | 81.75        |
| 321 | 2016-01-05 | 81.75 | 76.34 | 80.54 | 72.08 | ABOVE  | 81.75        |
| 320 | 2016-01-04 | 80.95 | 75.15 | 76.29 | 70.86 | ABOVE  | 81.75        |
+-----+------------+-------+-------+-------+-------+--------+--------------+

我如何计算 SQL 服务器中序列中组的最小值和最大值？

How do i calculate minimum and maximum for groups in a sequence in SQL Server?

sql

sql-server

group-by

gaps-and-islands