I have seen quite a few posts and questions lately from people that are trying to change the data in a view, or move data in a view.
A view has no data.
It’s that simple. If you have something like this in AdventureWorks:
SELECT firstname , lastname FROM HumanResources.vEmployee
And this view is defined as:
CREATE VIEW [HumanResources].[vEmployee] AS SELECT e.[EmployeeID] ,c.[Title] ,c.[FirstName] ,c.[MiddleName] ,c.[LastName] ,c.[Suffix] ,e.[Title] AS [JobTitle] ,c.[Phone] ,c.[EmailAddress] ,c.[EmailPromotion] ,a.[AddressLine1] ,a.[AddressLine2] ,a.[City] ,sp.[Name] AS [StateProvinceName] ,a.[PostalCode] ,cr.[Name] AS [CountryRegionName] ,c.[AdditionalContactInfo] FROM [HumanResources].[Employee] e INNER JOIN [Person].[Contact] c ON c.[ContactID] = e.[ContactID] INNER JOIN [HumanResources].[EmployeeAddress] ea ON e.[EmployeeID] = ea.[EmployeeID] INNER JOIN [Person].[Address] a ON ea.[AddressID] = a.[AddressID] INNER JOIN [Person].[StateProvince] sp ON sp.[StateProvinceID] = a.[StateProvinceID] INNER JOIN [Person].[CountryRegion] cr ON cr.[CountryRegionCode] = sp.[CountryRegionCode];
The SELECT statement is the same as running
SELECT c.[FirstName] ,c.[LastName] FROM [HumanResources].[Employee] e INNER JOIN [Person].[Contact] c ON c.[ContactID] = e.[ContactID] INNER JOIN [HumanResources].[EmployeeAddress] ea ON e.[EmployeeID] = ea.[EmployeeID] INNER JOIN [Person].[Address] a ON ea.[AddressID] = a.[AddressID] INNER JOIN [Person].[StateProvince] sp ON sp.[StateProvinceID] = a.[StateProvinceID] INNER JOIN [Person].[CountryRegion] cr ON cr.[CountryRegionCode] = sp.[CountryRegionCode];
Note this is exactly the same thing as the view definition with fewer columns included. Or it could be written like this:
SELECT firstname , lastname FROM ( SELECT e.[EmployeeID] ,c.[Title] ,c.[FirstName] ,c.[MiddleName] ,c.[LastName] ,c.[Suffix] ,e.[Title] AS [JobTitle] ,c.[Phone] ,c.[EmailAddress] ,c.[EmailPromotion] ,a.[AddressLine1] ,a.[AddressLine2] ,a.[City] ,sp.[Name] AS [StateProvinceName] ,a.[PostalCode] ,cr.[Name] AS [CountryRegionName] ,c.[AdditionalContactInfo] FROM [HumanResources].[Employee] e INNER JOIN [Person].[Contact] c ON c.[ContactID] = e.[ContactID] INNER JOIN [HumanResources].[EmployeeAddress] ea ON e.[EmployeeID] = ea.[EmployeeID] INNER JOIN [Person].[Address] a ON ea.[AddressID] = a.[AddressID] INNER JOIN [Person].[StateProvince] sp ON sp.[StateProvinceID] = a.[StateProvinceID] INNER JOIN [Person].[CountryRegion] cr ON cr.[CountryRegionCode] = sp.[CountryRegionCode] ) a
In this case I’ve moved the view definition into the FROM clause of my SELECT query.
A view is literally a stored query that you can use to make it easier to write code. There is no data in the view, so if you need to change the data, or “refresh” the data from another database, you need to move the data in the tables that are referenced in the VIEW.
Filed under: Blog Tagged: syndicated, T-SQL