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我有一张带有结构的表：

 CREATE TABLE [dbo].[rx](
            [pat_id] [int] NOT NULL,
            [fill_Date] [date] NOT NULL,
            [script_End_Date]  AS (dateadd(day,[dayssup],[filldate])),
            [drug_Name] [varchar](50) NULL,
            [days_Sup] [int] NOT NULL,
            [quantity] [float] NOT NULL,
            [drug_Class] [char](3) NOT  NULL,
            [ofInterest] bit
            CHECK(fill_Date <=script_End_Date
PRIMARY KEY CLUSTERED 
(
            [clmid] ASC
)


CREATE TABLE [dbo].[Calendar](
             [cal_date] [date] PRIMARY KEY,
[Year] AS YEAR(cal_date) PERSISTED,
[Month] AS MONTH(cal_date) PERSISTED,
[Day] AS DAY(cal_date) PERSISTED,
             [julian_seq] AS 1+DATEDIFF(DD, CONVERT(DATE, CONVERT(varchar,YEAR(cal_date))+'0101'),cal_date),
     id int identity);

我在这个查询中使用了这些表：

;WITH x 
     AS (SELECT rx.pat_id, 
                c.cal_date, 
                Count(DISTINCT rx.drug_name) AS distinctDrugs 
         FROM   rx, 
                calendar AS c 
         WHERE  c.cal_date BETWEEN rx.fill_date AND rx.script_end_date 
                AND rx.ofinterest = 1 
         GROUP  BY rx.pat_id, 
                   c.cal_date 
         --the query example I used having count(1) =2, but to illustrate the non-contiguous intervals, in practice I need the below having statement
         HAVING Count(*) > 1), 
     y 
     AS (SELECT x.pat_id, 
                x.cal_date 
                --c2.id is the row number in the calendar table. 
                , 
                c2.id - Row_number() 
                          OVER( 
                            partition BY x.pat_id 
                            ORDER BY x.cal_date) AS grp_nbr, 
                distinctdrugs 
         FROM   x, 
                calendar AS c2 
         WHERE  c2.cal_date = x.cal_date) 
SELECT *, 
       Rank() 
         OVER( 
           partition BY pat_id, grp_nbr 
           ORDER BY distinctdrugs) AS [ranking] 
FROM   y

日历表运行了三年，而 rx 表中有大约 800k 行。在前面的查询运行了几分钟后，我决定向它添加一个索引以加快速度。我添加的索引是

create index ix_rx
on rx (clmid)
include (pat_id,fill_date,script_end_date,ofinterest)

该索引对查询的运行时间影响为零。谁能帮助解释为什么没有使用上述索引？这是一个回顾性数据库，不会向其中添加更多数据。如果需要，我可以添加执行计划。

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2 回答 2

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clmid查询中根本不使用该字段。因此，如果优化器仅考虑包含列，我会感到惊讶。

如果要使用索引加快查询速度，请从使用表的查询开始。使用的字段是pat_id、drug_name、rx_ofinterest、fill_date和script_end_date。由于介于两者之间，最后两个具有挑战性。你可以试试这个索引： rx(pat_id, drug_name, ofinterest, fill_date, script_end_date).

拥有索引中的所有引用字段将可以在不加载数据页面的情况下访问数据。

于 2013-01-31T19:19:51.767 回答
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因为它不是一个合适的索引。创建两个索引，一个在 [pat_id] 上，另一个在 drug_name 上。——</p>

于 2013-01-31T19:20:29.243 回答