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我们大约每分钟收集一次关于三个不同服务器的数据，并将其存储在名为“DirectAccessStat”的 SQL Server Express 2019 表中。

我们需要每隔 15 分钟报告一次连接总数（跨三台服务器）。

我有一个有效的 SQL 查询，但速度很慢，需要有关如何改进查询或建议不同方法的提示。

数据格式：

Id     Server    Time                    Connections  CPU  Memory  Health
------ --------- ----------------------- ------------ ---- ------- -------
20250  Server3   2020-03-23 16:43:31.000 495          14   43      OK
20249  Server2   2020-03-23 16:43:29.000 550          20   75      OK
20248  Server1   2020-03-23 16:43:27.000 509          10   76      OK
20247  Server3   2020-03-23 16:42:24.000 494          8    43      OK
20246  Server2   2020-03-23 16:42:22.000 569          14   75      OK
20245  Server1   2020-03-23 16:42:20.000 510          20   76      OK
20244  Server3   2020-03-23 16:41:18.000 492          7    43      OK
20243  Server2   2020-03-23 16:41:16.000 565          11   75      OK
20242  Server1   2020-03-23 16:41:13.000 517          6    76      OK
20241  Server3   2020-03-23 16:40:11.000 495          14   43      OK
20240  Server2   2020-03-23 16:40:09.000 566          8    75      OK
20239  Server1   2020-03-23 16:40:06.000 519          16   76      OK
20238  Server3   2020-03-23 16:39:04.000 505          16   43      OK
20237  Server2   2020-03-23 16:39:02.000 574          12   75      OK
20236  Server1   2020-03-23 16:38:59.000 522          7    76      OK
20235  Server3   2020-03-23 16:37:57.000 515          10   43      OK
20234  Server2   2020-03-23 16:37:55.000 590          15   75      OK
20233  Server1   2020-03-23 16:37:52.000 523          6    76      OK
20232  Server3   2020-03-23 16:36:50.000 522          9    43      OK
20231  Server2   2020-03-23 16:36:47.000 583          15   75      OK
20230  Server1   2020-03-23 16:36:45.000 538          11   76      OK
20229  Server3   2020-03-23 16:35:43.000 520          10   43      OK
20228  Server2   2020-03-23 16:35:41.000 585          11   75      OK
20227  Server1   2020-03-23 16:35:38.000 539          8    76      OK
20226  Server3   2020-03-23 16:34:36.000 531          8    43      OK
20225  Server2   2020-03-23 16:34:34.000 602          17   75      OK
20224  Server1   2020-03-23 16:34:31.000 547          9    76      OK
20223  Server3   2020-03-23 16:33:28.000 533          9    43      OK
20222  Server2   2020-03-23 16:33:26.000 591          15   75      OK
20221  Server1   2020-03-23 16:33:24.000 545          11   76      OK

期望的输出（TotalConnections 是给定 15 分钟间隔后所有服务器的第一行的总和）：

Time             TotalConnections
---------------- ----------------
23.03 16:30      1703
23.03 16:15      1868
23.03 16:00      2046
23.03 15:45      2189
23.03 15:30      2336
23.03 15:15      2454
23.03 15:00      2531
23.03 14:45      2555
23.03 14:30      2621
23.03 14:15      2643
...

有效的 SQL，但速度很慢（并且每次迭代都作为新的子查询运行，因此输出很笨重..）：

-- Find last whole quarter
DECLARE @now DateTime = GetDate();
DECLARE @minute int = 0;
DECLARE @nowminute int = DATEPART(MINUTE, @now);

IF @nowminute > 45
    SET @minute = 45;
ELSE
    IF @nowminute > 30
        SET @minute = 30;
    ELSE
        IF @nowminute > 15
            SET @minute = 15;

-- Set start time to last whole quarter
DECLARE @lookTime DateTime = DATETIME2FROMPARTS(YEAR(@now), MONTH(@now), DAY(@now), DATEPART(HOUR, @now), @minute, 0, 0, 0);

-- Continue lookup until specified end datetime
DECLARE @endTime DateTime = DATEADD(WEEK, -1, @lookTime);

-- Output time parts
DECLARE @datepart varchar(10);
DECLARE @hourpart varchar(2);
DECLARE @minutepart varchar(2);

WHILE @lookTime > @endTime
BEGIN

    -- Set output time parts
    SET @datepart = CONVERT(varchar(5), @lookTime, 104);
    SET @hourpart = RIGHT('0' + CAST(DATEPART(HOUR, @lookTime) as varchar(2)), 2);
    SET @minutepart = RIGHT('0' + CAST(DATEPART(MINUTE, @lookTime) as varchar(2)), 2);

    SELECT (@datepart+' '+@hourpart+':'+@minutepart) AS [Time], SUM(D.Connections) AS TotalConnections
    FROM DirectAccessStat D
    INNER JOIN (
        -- Select minimum Id grouped by server, after selected looktime
        SELECT MIN(Id) AS Id
        FROM DirectAccessStat
        WHERE [Time] > @lookTime and [Time] < DATEADD(MINUTE, 20, @lookTime)
        GROUP BY [Server]
    ) AS I
    ON D.Id = I.Id;

    -- Subtract 15 minutes from looktime
    SET @lookTime = DATEADD(MINUTE, -15, @lookTime);
END
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2 回答 2

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感谢您的建议。我离开了 while 循环并使用纯 SQL 完成了它。从这个线程中得到灵感。

SELECT D2.Time, SUM(D2.AvgConnections) AS TotalConnections FROM (
SELECT
    MIN(D.Id) AS Id,
    [Server] AS Server,
    (
        RIGHT('0'+CAST(DATEPART(MONTH, D.[Time]) as varchar(2)), 2)
        + '.' + RIGHT('0'+CAST(DATEPART(DAY, D.[Time]) as varchar(2)), 2)
        + ' '+ RIGHT('0'+CAST(DATEPART(HOUR, D.[Time]) as varchar(2)), 2)
        + ':'+ RIGHT('0'+CAST(((DATEPART(MINUTE, D.[Time]) / 15) * 15) as varchar(2)), 2)
    ) AS [Time],
    AVG(Connections) AS AvgConnections
FROM DirectAccessStat D
GROUP BY
    [Server],
    DATEPART(YEAR, D.[Time]),
    DATEPART(MONTH, D.[Time]),
    DATEPART(DAY, D.[Time]),
    DATEPART(HOUR, D.[Time]),
    (DATEPART(MINUTE, D.[Time]) / 15)
) D2
GROUP BY D2.Time
ORDER BY D2.Time DESC

输出：

Time        TotalConnections
----------- ----------------
03.23 18:45 1089
03.23 18:30 1120
03.23 18:15 1154
03.23 18:00 1182
03.23 17:45 1207
03.23 17:30 1244
03.23 17:15 1321
03.23 17:00 1413
03.23 16:45 1511
03.23 16:30 1626
03.23 16:15 1785
03.23 16:00 1949
于 2020-03-23T17:58:50.583 回答
0

有一种 presudo SQL，因为我不熟悉 SQL Server 方言。我将使用 SQL Server 提供的一些命令，但无法修复查询：

SELECT intervalBeginning as "Time", COUNT(*) as "TotalConnections" 
FROM (
  SELECT DATEADD(minute, ROUND(DATEDIFF(minute, 0, Time) / 15.0, 0) * 15, 0) AS intervalBeginning
  FROM DirectAccessStat
) intervals
GROUP BY intervalBeginning 
ORDER BY intervalBeginning

它更快吗？我不知道，但是编写纯 SQL 有时要快得多，因为您不会弄乱数据库的内部结构，而是只需声明地告诉您需要什么，将优化留给查询优化器。

查询的作用是在内部查询中仅从给定数据中选择时间，但将此时间截断为最近的 15 分钟间隔。假设 SQL Server 支持选择重复项，我们会得到许多区间开始，其中一些是相同的。因此，在外部查询中，我们按这些区间起点分组，这允许我们输出单个区间起点并计算遇到的此类起点的总数。从过去到未来的排序间隔只是为了一个漂亮的输出

于 2020-03-23T16:14:14.490 回答