Everything About SQL Views with Examples

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 outs 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 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?

The view in SQL is the virtual tablet designed based on the other SQL state’s result set. Views are designed to mitigate complications associated with different tables. In addition, it can 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.

Also Read: SQL Tutorial

A virtual table whose contents are explained by the query is called a view in SQL. It comprises a set of rows and columns of data. The SQL view doesn’t exist as the database’s stored assortment of data values. The data columns and rows 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

They are extremely valuable if you want to learn about the importance of views. 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 to access underlying tables).

They are also used to offer a backward interface. In addition, they are also useful if you copy data from or to an SQL server.

Use of Views of 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 to hide 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 data security. They act as a security mechanism, allowing you to show or mask data based on security and requirements.
• Updating rows in a virtual table is easy, given that DBMS can translate the requests via 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 SQL views with the help of an example.

Different Types of Views

Considering the SQL Server, there are primarily two types of views in SQL, as highlighted below:

1. System-Defined View
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:

• Information Schema View
  There are 20 schema views, which display data information. The best example is the table. The view’s syntax begins with INFORMATION_SCHEMA. Note that it is succeeded by a view name such as INFORMATION_SCHEMA.[View Name].

• Catalogue View
  The next one is the catalogue views introduced in 2005 in SQL Server. They are divided into different groups and offer an excellent method for presenting, transforming, and obtaining data. They usually start with “sys.”

• Dynamic Management View
  The next and last type is the dynamic management view, which was introduced in 2005. In this view, an administrator can diagnose the SQL server by viewing details. There are two main subtypes: Database–Scoped and Server–Scoped.

2. 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 complex. 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 how 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:

Discussion of the Syntax and Examples of Creating Views in SQL

In SQL, the view is 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, you need to expand that database in that Object Explorer.

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.

Also Read: Mostly Asked DBMS Interview Questions (With Answers)

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 apply to each and every view. The updatable view allows the UPDATE command to be performed on itself. And it does not affect other tables.

Also Read: Constraints in SQL

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 if the view references are over one base table.

Dropping Views

While dropping the view, the view & other details about that view will be deleted. Permissions to view in SQL will be deleted. Any view on the table dropped by implementing the DROP TABLE should be dropped with DROP VIEW.

Know More: What is Arrays in Java | Everything You Need to Know

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 allows you to hide WHERE clauses 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

Conclusion

SQL Views are a powerful feature that enhances data security, simplifies complex queries, and improves database management. They act as virtual tables, allowing users to retrieve specific data without modifying the underlying tables. Views help in maintaining data abstraction, providing controlled access to sensitive information, and optimizing performance. However, they come with limitations, such as restrictions on updates in certain cases and potential performance overhead.

Understanding how to create, alter, update, and drop views is essential for efficient database design. When used effectively, views can significantly improve database efficiency and maintainability. To deepen your understanding of data management and analytics, consider enrolling in the Advanced Certification Program in Data Science & Analytics powered by University of Chicago.