Question

您可能知道，您无法使用自联接索引视图。实际上甚至是同一个表的两个连接，即使它在技术上不是自我连接。来自微软的几个人想出了一个解决方案。但它太复杂了我不明白!!!

问题的解决方案是：http://jmkehayias.blogspot.com/2008/12/creating-indexed-view-with-self-join.html

我想要应用此工作的视图是：

create VIEW vw_lookup_test
WITH SCHEMABINDING
AS
select
count_big(*) as [count_all],
awc_txt,
city_nm,
str_nm,
stru_no,
o.circt_cstdn_nm [owner],
t.circt_cstdn_nm [tech],
dvc.circt_nm,
data_orgtn_yr 
from 
((dbo.dvc 
join dbo.circt 
on dvc.circt_nm = circt.circt_nm) 
join dbo.circt_cstdn o
on circt.circt_cstdn_user_id = o.circt_cstdn_user_id)
join dbo.circt_cstdn t
on dvc.circt_cstdn_user_id = t.circt_cstdn_user_id
group by
awc_txt,
city_nm,
str_nm,
stru_no,
o.circt_cstdn_nm,
t.circt_cstdn_nm,
dvc.circt_nm,
data_orgtn_yr 
go

任何帮助都会有很大帮助!!!

提前非常感谢！

编辑：所以我发现这也行。请注意，我在第一个索引视图中连接到表一次，第二次在第二个非索引视图中连接到表。

alter VIEW vw_lookup_owner_test2
WITH SCHEMABINDING  
AS 
select
count_big(*) as [countAll],
awc_txt,
city_nm,
str_nm,
stru_no,
dvc.circt_nm,
circt_cstdn_nm,
data_orgtn_yr,
dvc.circt_cstdn_user_id
from dbo.dvc 
join dbo.circt
on dvc.circt_nm = circt.circt_nm
join dbo.circt_cstdn o
on circt.circt_cstdn_user_id = o.circt_cstdn_user_id
group by
awc_txt,
city_nm,
str_nm,
stru_no,
dvc.circt_nm,
circt_cstdn_nm,
data_orgtn_yr,
dvc.circt_cstdn_user_id
go

和

CREATE UNIQUE CLUSTERED INDEX [idx_vw_lookup_owner2_test1] ON [dbo].[vw_lookup_owner_test2] 
(
    [awc_txt] ASC,
    [city_nm] ASC,
    [str_nm] ASC,
    [stru_no] ASC,
    [circt_nm] ASC,
    [circt_cstdn_nm] ASC,
    [data_orgtn_yr] ASC,
    [circt_cstdn_user_id] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
GO

和

create view vw_lookup_dvc_loc
as
select
awc_txt,
city_nm,
str_nm,
stru_no,
circt_nm,
o.circt_cstdn_nm as [owner],
--o.circt_cstdn_user_id,
t.circt_cstdn_nm as tech,
data_orgtn_yr
from vw_lookup_owner_test2 o With (NOEXPAND)
join circt_cstdn t
on o.circt_cstdn_user_id = t.circt_cstdn_user_id
group by
awc_txt,
city_nm,
str_nm,
stru_no,
circt_nm,
o.circt_cstdn_nm,
data_orgtn_yr,
t.circt_cstdn_nm
--o.circt_cstdn_user_id

然后我可以根据自己的意愿在第一个视图上创建附加索引。我不确定这个解决方案（或者那个问题的解决方法）是否会真正加快性能，但我会告诉你。

Answer 1

以下是我从博客中获得的内容

假设你想在dbo.circt_cstdn加入2次，即你想要像
这样的东西
```
         owner       tech
rowA     a.nm        b.nm
...
```
不是将值分为2列，而是将其分为2行（上面每行2行），并添加一列以说明哪一行适用于哪一列。请注意，行1.1和行1.2具有相同的数据（名称和列除外）
```
         name   for
row1.1   nm     owner
row1.2   nm     tech
...
```
然后你转动所有者和技术的最大名称列。注意 - max函数只是为了欺骗PIVOT（需要一些聚合函数），如果只有一个记录，你可以使用任何返回相同值的聚合函数老板科技 row1 nm nm ...

现在，如果我们为您的查询执行此操作

创建一个表d，就像这个
```
 i
 1
 2
```

使用此

交叉加入查询的第一部分

SELECT 
     count_big(*) as [count_all], 
     awc_txt, 
     city_nm, 
     str_nm, 
     stru_no, 
     dvc.circt_nm, 
     data_orgtn_yr
FROM  
     dbo.dvc  
     INNER JOIN dbo.circt on dvc.circt_nm = circt.circt_nm
     CROSS JOIN dbo.d  
GROUP BY
     awc_txt, city_nm, str_nm, stru_no, dvc.circt_nm, data_orgtn_yr, d.i

现在让我们使用行为所有者，如果D.i是1，那么技术如果D.i是2

SELECT 
     count_big(*) as [count_all], 
     awc_txt, 
     city_nm, 
     str_nm, 
     stru_no, 
     dvc.circt_nm, 
     data_orgtn_yr,
     Case 
         WHEN d.i = 1 THEN 'Owner'
         WHEN d.i = 2 THEN 'Tech'
     END
FROM  
     dbo.dvc  
     INNER JOIN dbo.circt on dvc.circt_nm = circt.circt_nm
     CROSS JOIN dbo.d 
GROUP BY
     awc_txt, city_nm, str_nm, stru_no, dvc.circt_nm, data_orgtn_yr, 
     Case 
         WHEN d.i = 1 THEN 'Owner'
         WHEN d.i = 2 THEN 'Tech'
     END

现在添加nm列。要获得名称，如果它是所有者行（d.i = 1），则加入circt_cstdn，如果是技术行（d.i = 2），则加入dvc。注意 - 我在此处尝试了一个快捷方式，将其置于连接条件中。如果它不起作用，请尝试使用博客文章方式（在circt.circt_cstdn_user_id OR dvc.circt_cstdn_user_id上进行连接，然后使用WHERE子句进行过滤）

SELECT 
     count_big(*) as [count_all], 
     awc_txt, 
     city_nm, 
     str_nm, 
     stru_no, 
     dvc.circt_nm, 
     data_orgtn_yr,
     Case 
         WHEN d.i = 1 THEN 'Owner'
         WHEN d.i = 2 THEN 'Tech'
     END as PersonType,
     circt_cstdn_nm
FROM  
     dbo.dvc  
     INNER JOIN dbo.circt on dvc.circt_nm = circt.circt_nm
     CROSS JOIN dbo.d 
     INNER JOIN dbo.circt_cstdn on circt_cstdn_user_id = 
          CASE
               WHEN d.i = 1 THEN circt.circt_cstdn_user_id
               WHEN d.i = 2 THEN dvc.circt_cstdn_user_id
          END
GROUP BY
     awc_txt, city_nm, str_nm, stru_no, dvc.circt_nm, data_orgtn_yr, 
     Case 
         WHEN d.i = 1 THEN 'Owner'
         WHEN d.i = 2 THEN 'Tech'
     END,
     circt_cstdn_nm

使用该视图创建视图并创建索引

create VIEW vw_lookup_test_imed
WITH SCHEMABINDING 
AS
    <<query above>>  
GO

spell to create INDEX

现在您可以将PersonType列转换为所有者和技术列

SELECT 
     count_all, 
     awc_txt, 
     city_nm, 
     str_nm, 
     stru_no, 
     dvc.circt_nm, 
     data_orgtn_yr,
     [Owner], 
     [Tech] 
FROM 
( 
     SELECT 
          count_all, 
          awc_txt, 
          city_nm, 
          str_nm, 
          stru_no, 
          dvc.circt_nm, 
          data_orgtn_yr,
          PersonType,
          circt_cstdn_nm
     FROM dbo.vw_lookup_test_imed WITH (NOEXPAND) 
) src 
PIVOT 
( 
     MAX(circt_cstdn_nm) 
     FOR PersonType IN ([Owner], [Tech]) 
) pvt

如果存在语法错误（由于我现在无法访问数据库，因此必然会有很多错误）请告诉我。

Answer 2

我认为这种JOIN语法很糟糕，并且源自MS Access。啊。我建议你使用：

select
count_big(*) as [count_all],
awc_txt,
city_nm,
str_nm,
stru_no,
o.circt_cstdn_nm [owner],
t.circt_cstdn_nm [tech],
dvc.circt_nm,
data_orgtn_yr 

-- HERE
from dbo.dvc
join dbo.circt on (dvc.circt_nm = circt.circt_nm) 
join dbo.circt_cstdn o on (circt.circt_cstdn_user_id = o.circt_cstdn_user_id)
join dbo.circt_cstdn t on (dvc.circt_cstdn_user_id = t.circt_cstdn_user_id)

group by
awc_txt,
city_nm,
str_nm,
stru_no,
o.circt_cstdn_nm,
t.circt_cstdn_nm,
dvc.circt_nm,
data_orgtn_yr

这种语法更清晰，更易于理解，并且在SQL Server，Firebird，Oracle，MySQL和其他许多方面都得到了认可。现在你可以更好地看到“表格”之间的关系。当您加入相同的“表”两次或更多次时，您需要为每个“表”添加别名。在一行“circt_cstdn”别名为“o”。另一方面，“circt_cstdn”别名为“t”。

我建议使用LEFT JOIN或INNER JOIN代替JOIN。

自我加入问题需要一些认真的帮助

2 个答案: