视图中每一列的源列是啥

Posted 2023-02-26

【中文标题】视图中每一列的源列是啥

【英文标题】：What is the source column of each column in view视图中每一列的源列是什么

【发布时间】：2017-10-24 21:08:29

【问题描述】：

我如何知道视图中的每一列，或处理源列 例如， 我有这张桌子：

CREATE TABLE [dbo].[tbl_Address](
    [iAddressId] [int] IDENTITY(1,1) NOT NULL,
    [nvStreet] [nvarchar](50) NULL,
    [iHouseNum] [int] NULL,
    [nvEnterance] [nvarchar](10) NULL,
    [iFloor] [int] NULL,
    [nvNeighberwood] [nvarchar](20) NULL,
    [nvCity] [nvarchar](20) NULL,
    [nvNote] [nvarchar](50) NULL,
 CONSTRAINT [PK_tbl_Address] PRIMARY KEY CLUSTERED 
(
    [iAddressId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

还有这个观点：

CREATE VIEW ViewALIAS
AS
SELECT a.nvStreet myStreet,a.nvCity manyStreeats FROM tbl_Address a  

必填答案：

nameObject | nameColumn | SourceObject | SourceColumn  
----------------------------------------------------- 
tbl_Address| nvStreet   | ViewALIAS    | myStreet  
tbl_Address| nvCity     | ViewALIAS    | manyStreeats

我知道如何制作列：nameObject、nameColumn、SourceObject 或表：nameObject、SourceObject、SourceColumn 但我不知道如何匹配 x 和 t

【问题讨论】：

必须为视图解析系统表源才能获取该数据。

为什么需要这样做？

我做一个插件

【参考方案1】：

我认为你不能得到你想要的东西（见下面的解释），但你可以得到一个近似值，首先你可以使用以下方法获取视图的所有列：

select name, column_id from sys.columns where object_id=object_id('ViewALIAS')

然后您可以使用column dependencies 获取视图引用的列，注意这包括查询的任何部分中使用的所有列，而不仅仅是选择列表中的列（例如，它会列出使用的列在WHERE 条件下）：

select dependencies.referenced_entity_name as referenced_name,
  entities.referenced_minor_id as column_id, entities.referenced_minor_name as column_name
from sys.sql_expression_dependencies as dependencies
join sys.objects as objects on object_id=referencing_id
join sys.schemas as schemas on schemas.schema_id=objects.schema_id
cross apply sys.dm_sql_referenced_entities(schemas.name+'.'+objects.name,'OBJECT') as entities
where entities.referenced_entity_name=dependencies.referenced_entity_name
  and (is_schema_bound_reference=0 or entities.referenced_minor_id=dependencies.referenced_minor_id)
  and entities.referenced_minor_id!=0
  and referencing_id=object_id('ViewALIAS')

您无法链接这两个结果，因为据我所知，SQL Server 中无法获取 object catalog views 中的视图列和引用列之间的关系，我不知道确切原因，但我很确保主要原因是视图列几乎可以是任何东西，因此并不总是可以将其与表列匹配，举几个例子：

CREATE VIEW ExampleView AS
SELECT ID, -- table column
  (Value1+Value2)*Value3 as Total, -- multiple columns
  12345 as Value, -- literal value
  getdate() as CurrentDate, -- scalar function
  dbo.fnMyFunction(Value1,Value2) as ScalarColumn, -- scalar function with parameters
  TableFunctionColumn, -- column from a table function (which can be almost anything)
  CASE WHEN Value1<10000 THEN Value2
    WHEN Value1>20000 THEN Value3
    ELSE Value2+Value3 END AS CaseColumn, -- different columns based on another value
  (SELECT SUM(OtherValue) FROM OtherTable
    WHERE OtherID=ID GROUP BY OtherValue) AS SubqueryColumn -- subquery result
FROM ExampleTable
CROSS APPLY dbo.fnTableFunction(ID)

我认为CASE列是最具代表性的例子，因为视图列使用的表列依赖于another列的值，而该列的值不直接用于列值。