In this article, we will look at views in SQL, their creation process and the benefits that they bring. We also explain at what time and for what purpose you would create and use views in your database management.
What do you understand about Views?
Views are a bit tricky; basically, it is defined as a stored SQL command that uses the data contained in tables, subqueries or other views to present a virtual table for the user. As we know every query has data and when a user wants to see that data, the user selects it. But when a user saves the query as a view, it will not store the data, instead it will return the data each time using the saved query. This approach gives the user a kind of limited window on the particular data needed out of all the existing data in the database.There can be so many fundamental reasons why one might want to create a view but among many the most prominent one is to ease the complexity and help visualize. Imagine having a huge dataset where a single query is unable to get all the information. By using views, you can use much more simplified commands and get the same output. So this way Views would also be able to enhance security since they can restrict where a user wants to search for a query to a single or multiple columns and rows.
How to Make a View
The process of creating a view in SQL is almost hassle-free. You start with the ‘CREATE VIEW’ clause together with the name of the view and the query that instantiates it. The general principle formula is as follows:sql
CREATE VIEW view_name AS
SELECT column1, column2, ... FROM table_name
WHERE condition;
Kinds of Views
In SQL, there are a good number of views, and these different kinds of views can enhance your work in the following ways:1. Simple Views:
A simple view is created from a single table, with the underlying view definition implemented purely using the select statement with no join, union nor any grouping. It is primarily employed in retrieving specific columns or rows from the table.2. Complex Views:
A complex view is a view that is built from two or more tables usually by a join operation. Complex views can be advantageous as they allow you to search for data scattered over multiple databases and present them in a single view.3. Updatable Views:
With these views, you can edit the tables that the view is based on. But there are some views that are not updatable. For instance, if the view processes more complicated data such as joins, aggregate or grouping data, then the view would not be updatable.4. Materialized Views:
In contrast to normal views that offer a look at data without keeping it anywhere, materialized views do keep the data which is the output of the query one has made. This comes in handy especially when there are complicated queries to make, or one has big amounts of data. Of course, the downside is that the materialized view needs to be refreshed after some time in order for its contents to be updated.
Benefits of Using Views
SQL has a lot of advantages, especially when views are taken into consideration. Some of the top ones include:1. Simplification of Complex Queries:
If you’re dealing with complex queries that are used oftentimes, it is better to write them out in views which will make your SQL a lot easier to work with. Views will allow you to cut down the amount of long queries you would otherwise have to keep writing and instead reference ‘the view’: which will save you time as well as making it more efficient and less prone to errors.2. Data Security:
Users can create views and limit aspects of the data that can be used. For instance, when a user has a table that contains confidential data like employee salaries, the user can create a view which only displays the columns that the users are meant to see.3. Enhanced Database Handling:
Through the concept of Views, data can be presented in a way that is meaningful or can be comprehended with ease. For example, you can make a view that is a union of different tables and makes presentation of data much simpler. This can be quite useful especially in the case of big databases where interdependencies among various tables are complicated.4. Elimination of Discrepancies:
Views allow uniformity in the reporting and the querying. For instance, if the same queries are done repeatedly, then the use of views will enable that whenever a user or an application invokes the view, the output will be homogenous and without variation.5. Concealment of Business Logic:
A lot of complex business logic can be very well contained in a view, in which case, the considerables of the query issued to the developer and the users won't have to handle the complexity of the query. They are therefore shielded from the logic thus making their dealings with the database uncomplicated.Working With Views
When the view is created, there are instances when it may be essential to change or update it. You can change an existing view with the help of `CREATE OR REPLACE VIEW` statement. This means that you can alter the definition of a view without dropping the view first and then creating it again.sql
CREATE OR REPLACE VIEW view_name AS SELECT column1 ,column2 ,.... FROM table_name WHERE condition;
Update data via views
Using views has its pros and cons, they help to structure and compile queries, but it comes with updatable views. As a general rule single table simple views, which do not involve any complex operations, are updatable. In other words, you might be able to run 'INSERT`, `UPDATE`, and DELETE` on the view, and those modifications will reflect in the base table. But, it is possible that the view with defined joins, aggregations, and distinct selections might not be allowed to edit, update functionalities. You won’t be able to change the data even by using the view. So, rather than modifying data in a table view, you would interact with underlying tables.Performance rules of thumb
Although views are quite helpful and convenient, there are a few important performance considerations that must be taken into account. It will be important to note at this point that a view does not contain any data – every time a view is queried, SQL has to go and execute the query which may prove costly in some scenarios. For example, a single table query might take longer to execute compared to a complex view that joins many large tables.However, these problems can be avoided through the use of materialized views, which enable users to speed things up as there is no need to recalculate the view every time it is queried. The only drawback is that the materialized views need frequent updating to avoid outdated data from being used.
