Are you planning to opt for a full stack development course? Before anything else, you need to learn about SQL view. Let's discover the ins and out in the following guide.
SQL views are in the form of virtual tables. It consists of columns and rows in a database. It is created by choosing fields from tables that are present in a database. The view may have rows or specific rows depending on some conditions. Let's learn more about what is a view in SQL in the following points:
What is View in SQL?
Talking about the view in SQL, it happens to be the virtual tablet designed on the basis of the other SQL state's result set. Views are designed with the intention of mitigating complications associated with different tables. In addition to that, it can also deliver data in the most simplified manner. The view in SQL can allow you to maintain data integrity & offer data security. As a result, it acts as the perfect security mechanism.
One quick note: Discover the ins and out of polymorphism-in-java.
How Does a SQL View Work?
A view in SQL is nothing but a virtual table whose contents are elucidated by the query. It comprises a set of rows and columns of data. The SQL view doesn't exist as the stored assortment of data values in the database. The columns and rows of the data come from different tables in a query that defines the view. They are produced if the view has been referenced.
Importance of View in SQL
If you want to learn about the importance of views, well, they are extremely valuable. Views do everything between focusing, simplifying, and customizing the perception every user has regarding any database. Altogether, SQL views are used as security mechanisms by allowing users to access data via the view (that too without granting permission for accessing underlying tables).
They are also used for offering a backward interface. In addition, they are also useful if you copy data from or to an SQL server.
Use of Views in SQL
Want to know the use of views in SQL? Highlighted below are the uses of view in SQL:
- They can reduce the complexities of multiple tables, thereby simplifying data. They are used for hiding data complexity in a database.
- Another important benefit is that SQL views can take little storage as the database comprises a view's statements instead of a copy of tables.
- Views also offer security to data. What it does is act as a security mechanism. They allow you to show data or mask them based on security and requirements.
- Updating rows in a virtual table is so easy, given that DBMS can translate the requests via the views.
- The next and last benefit is that SQL views maintain data integrity. Not to forget, it presents a consistent & accurate data image from a database even when underlying sources are restructured, split, or renamed.
Examples of View in SQL
Let’s understand a view in SQL with the help of an example.
Create a View
CREATE VIEW us_customers AS
SELECT customer_id, first_name
WHERE Country = 'USA';
Update a View
CREATE OR REPLACE VIEW us_customers AS
WHERE Country = 'USA';
Delete a View
DROP VIEW us_customers;
Different Types of Views
Considering the SQL Server, there are primarily two types of views in SQL, as highlighted below:
The system-defined view is the pre-established view. It exists in the SQL Server's Master Database. It acts as a template for tables and data.
The system-defined view in SQL can be classified into three forms:
User Defined View
User-defined view comprises the following types:
- Simple View
This type of SQL view is based on one table. These operations include the delete and update options.
- Complex View
The next is the complex view. When the view is created from over one table, it is a complex view. This type of view contains group data. And the operations of update, insert, and delete are impossible here.
How to Create a View in SQL?
After learning the types of views in SQL, it is time to learn the steps to create the SQL view. Creating a view in SQL is very easy. You simply need to follow these points:
- Specify CREATE VIEW and give a name to that view.
- Now, you need to define the SELECT
Here's noting down the example:
CREATE VIEW VProductSpecialList
select p.ProductID AS [ProductIdNumber] ,
p.Name AS [ProductName],
p.ProductNumber [ProductMainNumber] from [Production].[Product] p
WHERE ProductID >900
Discussion of the Syntax and Examples f Creating Views in SQL
In SQL, the view happens to be the virtual table depending on the SQL statement's result set. The SQL view has columns and rows, just like one real table. The fields are from one (or more) real tables in a database.
How to Alter and Drop a View?
To alter or delete the view in SQL, you need to follow the given steps:
Step 1: Firstly, you need to open SSMS & connect to a database with that view
Step 2: Now, in that Object Explorer, you need to expand that database.
Step 3: Right-click on that view & tap on Design.
Step 4: Now, you need to make modifications to that view by deleting or adding columns/elements from that view
After this, you may choose additional columns from a different table.
To delete the view, follow these steps:
Step 1: First, connect to a database that has the view for modification.
Step 2: Expand that database in the Object Explorer.
Step 3: After this, right-click on the view name that you want to delete
Step 4: Tap on OKAY in that Delete Object box.
How to Use a View in SQL?
Considering the use of views in SQL, a view in SQL has columns and rows just like the real table. The fields in the view are from one or even more tables in a database. You may add SQL functions and statements to the view & present the data such that it is coming from a single table. The view is then created with the statement mentioning: CREATE VIEW.
Explanation of how to update a view in SQL
If you wish to update the view in SQL, you need to remember to follow these steps:
- Please include a primary key of a table
- Never use subqueries
- Clauses, distinct groups cannot be used when defining the view in SQL
- Discussion of the syntax and examples of updating views
Note that not every view in SQL can be updated. Thus, the UPDATE command will not be applicable to each and every view. The updatable view is the one that allows performing the UPDATE command on itself. And it does not affect other tables.
Inserting Rows into a View
You may insert rows into the view in SQL if it is a modifiable view. Note that it should not contain any derived column.
Deleting Rows into a View
You won't be able to delete a single row if the SQL view references over one base table. You may only update the columns belonging to one base table. You can insert the row and scroll down to the rows' end, thereby inserting the new values. Remember one thing: you won't be able to insert one row in case the view references over one base table.
While dropping the view, the view & other details about that view will be deleted. Permissions for the view in SQL will be deleted. Any view on the table dropped by implementing the DROP TABLE should be dropped with DROP VIEW.
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Advantages of using views in SQL
Here are the advantages:
- Seamless to make changes to any underlying table structure
- Using a view in SQL to return data from the tables allow you to hide WHERE clause or columns
- You may write simplified select statements against views, thereby handling complicated joins and queries
Disadvantages of using views in SQL
Here are the disadvantages:
- Make SQL queries complex & challenging to understand
- Slows down the queries and reduces the performance
- Limited views and certain tasks cannot be performed (like updating or inserting data)
- Imposes security risks when they aren't secured
- Difficult to maintain, specifically when used in complicated queries based on data from different tables
So, this post has given you compiled information on everything based on SQL view. Let's now highlight the most important FAQs related to the view in SQL.