嵌套视图性能

Question

我有这个SQL查询:

SELECT Start,
    ISNULL((SELECT Orders FROM [pp].dbo.VW_BEZETTING_RAW b2 WHERE b2.Start=b1.Start AND Afdeling = 'WP'),0) AS Werkplaats_ord,
    ISNULL((SELECT Tijd FROM [pp].dbo.VW_BEZETTING_RAW b2 WHERE b2.Start=b1.Start AND Afdeling = 'WP'),0) AS Werkplaats_tijd, 
    ISNULL((SELECT Orders FROM [pp].dbo.VW_BEZETTING_RAW b2 WHERE b2.Start=b1.Start AND Afdeling = 'MAG'),0) AS Magazijn_ord,
    ISNULL((SELECT Tijd FROM [pp].dbo.VW_BEZETTING_RAW b2 WHERE b2.Start=b1.Start AND Afdeling = 'MAG'),0) AS Magazijn_tijd, 
    ISNULL((SELECT Orders FROM [pp].dbo.VW_BEZETTING_RAW b2 WHERE b2.Start=b1.Start AND Afdeling = 'SERV'),0) AS Service_ord,
    ISNULL((SELECT Tijd FROM [pp].dbo.VW_BEZETTING_RAW b2 WHERE b2.Start=b1.Start AND Afdeling = 'SERV'),0) AS Service_tijd, 
    ISNULL((SELECT Orders FROM [pp].dbo.VW_BEZETTING_RAW b2 WHERE b2.Start=b1.Start AND Afdeling = 'CNC'),0) AS Draaibank_ord,
    ISNULL((SELECT Tijd FROM [pp].dbo.VW_BEZETTING_RAW b2 WHERE b2.Start=b1.Start AND Afdeling = 'CNC'),0) AS Draaibank_tijd, 
    ISNULL((SELECT Orders FROM [pp].dbo.VW_BEZETTING_RAW b2 WHERE b2.Start=b1.Start AND Afdeling = 'SECL'),0) AS Bougiekabels_ord,
    ISNULL((SELECT Tijd FROM [pp].dbo.VW_BEZETTING_RAW b2 WHERE b2.Start=b1.Start AND Afdeling = 'SECL'),0) AS Bougiekabels_tijd 
FROM [pp].dbo.VW_BEZETTING_RAW b1
GROUP BY Start

我可以解释一下我的查询的作用,但我不认为这是相关的,因为查询已经正常工作.我唯一的问题是处理时间; 我必须等待20-25秒才能获得结果,我认为这有点长.

什么SQL服务器似乎做(我认为),是SELECT我的价值观从视野中11次[pp].dbo.VW_BEZETTING_RAW(10次,我的每个子查询和1周时间我的正常查询).这是一项繁重的任务,因为SELECT * FROM [pp].dbo.VW_BEZETTING_RAW处理时间约为2秒.SELECT它不是必需的,它应该足以引用它一次并在每个子查询中使用结果.我测试了我的性能问题是否真的是因为子查询,它是:当我将查询减少到只有2而不是10个子查询时,处理时间只有6-7秒.

仅供参考,以下是结果的一部分[pp].dbo.VW_BEZETTING_RAW:

    Start       Afdeling    Orders  Tijd
    2013-05-14  SERV        3       0
    2013-05-14  WP          17      0
    2013-05-15  MAG         1       0
    2013-05-15  SERV        3       0
    2013-05-15  WP          14      0
    2013-05-16  CNC         1       0
    2013-05-16  MAG         9       0
    2013-05-16  SERV        3       0
    2013-05-16  WP          22      0
    2013-05-17  MAG         19      0
    2013-05-17  WP          8       0
    2013-05-20  MAG         11      0

我明确的问题是:是否有可能只有一次SELECT结果[pp].dbo.VW_BEZETTING_RAW并在每个子查询中使用this的结果(而不是SELECT再次触发此查询10次),或者,如果不可能,还有其他方法可以减少处理我查询的时间？

Answer 1

此查询应解决您的问题(包括您是否可以有负的订单/时间值).

SELECT Start,
    ISNULL(MIN(CASE WHEN Afdeling = 'WP' THEN Orders END),0) AS Werkplaats_ord,
    ISNULL(MIN(CASE WHEN Afdeling = 'WP' THEN Tijd END),0) AS Werkplaats_tijd, 
    ISNULL(MIN(CASE WHEN Afdeling = 'MAG' THEN Orders END),0) AS Magazijn_ord,
    ISNULL(MIN(CASE WHEN Afdeling = 'MAG' THEN Tijd END),0) AS Magazijn_tijd, 
    ISNULL(MIN(CASE WHEN Afdeling = 'SERV' THEN Orders END),0) AS Service_ord,
    ISNULL(MIN(CASE WHEN Afdeling = 'SERV' THEN Tijd END),0) AS Service_tijd, 
    ISNULL(MIN(CASE WHEN Afdeling = 'CNC' THEN Orders END),0) AS Draaibank_ord,
    ISNULL(MIN(CASE WHEN Afdeling = 'CNC' THEN Tijd END),0) AS Draaibank_tijd, 
    ISNULL(MIN(CASE WHEN Afdeling = 'SECL' THEN Orders END),0) AS Bougiekabels_ord,
    ISNULL(MIN(CASE WHEN Afdeling = 'SECL' THEN Tijd END),0) AS Bougiekabels_tijd 
FROM [pp].dbo.VW_BEZETTING_RAW b1
GROUP BY Start