在自我加入问题上需要一些认真的帮助

Question

您可能知道，您无法使用自连接索引视图。实际上，即使是同一张表的两个连接，即使它在技术上不是自连接。微软的几个人想出了一个解决方法。但是太复杂了，看不懂！！！

问题的解决方法在这里：http://jmkehayias.blogspot.com/2008/12/creating-indexed-view-with-self-join.html

我想将此工作应用于的视图是：

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

任何帮助将不胜感激！！！

提前非常感谢！

编辑：所以我发现这也可以。请注意，我在第一个索引视图中加入了一次表，第二次在第二个非索引视图中加入。

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

然后我可以根据需要在第一个视图上创建附加索引。我不确定这个解决方案（或解决这个问题的解决方法）是否真的会加快性能，但我会告诉你的。

Answer 1

这是我从博文中得到的信息

• 假设您想在 dbo.circt_cstdn 上加入 2 次，即您想要类似的东西

           owner       tech
  rowA     a.nm        b.nm
  ...
  

• 不是将值放入 2 列，而是将其放入 2 行（上面每行 2 行）并添加一个额外的列来说明哪一行是哪一列。注意第 1.1 行和第 1.2 行的数据相同（名称和列除外）

           name   for
  row1.1   nm     owner
  row1.2   nm     tech
  ...
  

• 然后您以所有者和技术人员的名称列的最大值为轴。注意 - max 函数只是为了欺骗 PIVOT（需要一些聚合函数），如果只有一条记录，您可以使用任何返回相同值的聚合函数 所有者技术 行 1 纳米 纳米 ...

现在，如果我们为您的查询这样做

1. 创建一个表d，像这个

    i
    1
    2
   

2. 用这个交叉连接查询的第一部分

   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
   

3. 现在让我们在 D.i 为 1 时使用所有者的行，如果 D.i 为 2 则使用技术

   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  
   

4. 现在添加 nm 列。要获得名称，如果它是所有者行 (d.i = 1)，则使用 circt 加入 circt_cstdn，如果是技术行 (d.i = 2)，则使用 dvc。注意 - 我在这里尝试了一个快捷方式，将它放在连接条件中。如果不行，试试博文的方式（在 circt.circt_cstdn_user_id OR dvc.circt_cstdn_user_id 上加入，然后使用 WHERE 子句过滤掉）

   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
   

5. 使用它创建一个视图并创建索引

   create VIEW vw_lookup_test_imed
   WITH SCHEMABINDING 
   AS
       <<query above>>  
   GO
   
   spell to create INDEX
   

6. 现在您 PIVOT 将 PersonType 列转换为 Owner 和 Tech 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 
   

如果有语法错误（肯定有很多，因为我现在无法访问数据库）请告诉我。

Answer 2

我认为这种 JOIN 语法很糟糕，起源于 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 

这种语法更简洁、更易于理解，并且在 SQL Server、Firebird、Oracle、MySQL 和许多其他工具中得到认可。 现在您可以更好地看到“表”之间的关系。 当您两次或多次加入同一个“表”时，您需要为每个表添加别名。在一行中，“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。