Database Administrator Tips – Defining Different Types Of Views
In an application, a view is simply the logical result grouping of an existing stored query on the current data, that the application users can query as they would on a persistent storage object. This implied query command is stored in the database hierarchy. Every application has a single view, and it’s called a session, which can be viewed by any user at any time.
Views can be defined as an association between views and commands. A view on a table represents the queryable data contained in that table. Similarly, a view on a collection represents the logical structure of the collection and can be specified to return all or part of the information contained in the values of its keys. views can also be used to provide applications with information about the relationship of two objects, for example, to create a queryable view that returns a list of objects where each object is associated with a different view.
Views are a great tool for creating reusable views that can be reused over again. For example, consider a previous scenario where you had created a static table, and then used an sql query to retrieve the values of the columns in the cell. When you subsequently created a view to represent these values, you created a new view that had all the same information as the old view, but could be used again if required. Of course, you have to remember to update both views whenever necessary. The problem with this scenario is that it requires the developer to refer to the original source code to find out how to use their view. More importantly, if you were to make any changes to your source code during the lifetime of your view, the update would not be reflected in your view, and your application would be unable to continue running.
An example of a view can illustrate the problem even more clearly – imagine you have a web form on your website that collects user details. If you were to add a new field called’s_id’ to the form, and then create a query to return the details of every user who has submitted a request for more information, you would need to update this view when the details changed. This scenario is illustrated clearly in the second example – once the details stored in the student details view change, you will need to update the view to reflect this change. However, what if you forget to update the details view before the change? Now the details stored within the view are not updated when the new s_id value is populated, resulting in the application becoming confused and unable to continue.
The second major advantage of using views is that they allow users to not only edit multiple tables but to easily switch between them at any time. As an example, if you have a business that sells products through eBay, and have many different sales listings for each item, it would be extremely tedious to update all of these listings separately. Instead, database administrators can run a series of view queries, updating all the relevant fields as required. In short, it provides a powerful solution for making any number of changes without being forced to rewrite code.
Views also provide the ability for database administrators to define visibility, or private visibility. Within a view, you define how rows are displayed to the end user, or how they are displayed to other views. To illustrate, if a view displayed all relevant columns to the user when updating a query, the end user would be unable to see the hidden rows of off-screen data. Within a protected view, the rows can still be viewed, but are hidden from view by an opaque session cookie. This allows for both better performance and better security, since any view can be created without requiring the knowledge of the current user.
Perhaps the most fundamental difference between these two types of views is how they interact with the rest of the system. A view is a view on a single table and can be used to alter or view any other table, even if it is not a view on a view. A protected view, however, is used to alter or hide a particular column within a single table. In this way, it can help maintain the performance of a system where changing the behavior of one table can alter another entire system.
Multiple views can be defined on a single database. The two types of views will share some common functionality, such as being able to directly access the base table. However, they differ in that only one instance of each view must exist on a single table. In simple terms, the view on the “base” table could be updated, and the view on “one” would become hidden and need to be redefined. The update to the “hidden” view would then need to be done, which would make the two view types incompatible with one another.
