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General

SQL Views

SQL Views

Introduction

SQL stands for the structured query language. It is the most basic language for dealing with various relational databases. SQL is used to insert, update, search and delete database records.  SQL is an ANSI standard language, and there are many different versions of this language. All the relational database management systems like MySQL, MS Access, Oracle, and Informix use this standard tool for data interpretation.

Applications of SQL

Some of the main applications for SQL are:

Retrieving Information

This language is capable of retrieving information within the database for processing transactions. The most widely used elements are select, insert, update, add, delete, truncate, alter and create.

Queries through Analytics

Data analysts use SQL for setting and running queries regularly.

Integrating Data

The primary function is to write data integration scripts that are used by database administrators.

Other applications

The users can do modifications to the index structures and tables. Moreover, it is also possible to add, update and delete the rows by employing this language.

Why should you use SQL?

SQL has several benefits, and the use of this programming language is growing in numbers. As companies collect more data, there would be a need to store this information. SQL quickly steps into the shoes of efficiently storing information and keeping records of large databases.

This structured query language runs on PCs, laptops, servers and also on your smartphone. It is an extremely flexible language that can be moved from one device to another.

  • The coding is done in English, and so it is easier to learn and understand this programming.
  • SQL is used by major vendors like IBM and Microsoft, who develop DBMS structures.
  • This language can be used to write programs using the databases.
  • SQL is an open-source language and has a large user community which can make the system less expensive than its competitors.
  • Language can be used across different architectures, including three-tiered internet architectures.
  • SQL offers different data views of the structures which are based on the input provided by the user.
  • SQL supports client-server architecture links front end computers with their respective servers.

Introduction to SQL Views

SQL uses views to interpret your relations databases. There are other ways to see the data on the tables like using the select statement with join or union clauses. SQL views are nothing but virtual tables that are produced by setting up a query command. The relational databases store the information as Select in the database query log. A view contains all the rows from the table or only the selected rows from the table. It is also possible to produce multiple views for a meal. Views allow the user to structure data into natural and intuitive classes, and it can also help to prevent access to visible data and to modify only what is required. Views also help to summarize data from the multiple tables and used to prepare reports.

Creating, deleting, inserting and updating your views

In this section, you are going to look at some examples of creating, deleting and ways to update your views. Let’s go and check them out:

Creating Views in SQL

For using this view, you need to use the create view command as write this statement:

Create view:
View_name AS
Select  column1, column2
From table_name
Where[condition];

It is also possible to create multiple tables using the select common as is SQL SELECT query.

IDNameAgeAddressSalary
1Sonam25Salt lake22000
2Rishi26Dum dum 23000
3Raju26Ultadanga25000
4Priyanka27Kalyani23500

Creating a view from the table, you will get:

CREATE VIEW EMPLOYEE_VW AS
SELECT NAME, AGE, SALARY
FROM EMPLOYEE

From the overhead view, the following column will be generated:

SELECT * FROM EMPLOYEE_VW

It is possible to create views from one more table

NameAgeSalary
Sonam2522000
Rishi2623000
Raju2625000
Priyanka2723500

Updating views in SQL

It is also possible to update views, but there are certain conditions that need to be fulfilled.

The SELECT should not contain:

  • Set function
  • Summary function
  • Keyword DISTINCT
  • Order by clause
  • Set operators

The FROM clause should not have multiple tables

There should be no subqueries in the WHERE clause

HAVING and GROUP BY should not be present

No updated calculated columns

It is important to insert ALL NOT NULL columns from the base table into the Insert query function

The Syntax should be:

CREATE OR REPLACE VIEW view _name AS
SELECT column1, column2
From table_name
Where[condition]

So if we want to see the department name, the table should look like this.

IdNameDeptname
1SonamHR
2RishiFinance
3RajuOperations
4PriyankaSales

To add the location column, we need to update the view as:

Create or replace view dept_view as

Select employee.id, employee.name,

Department.dept name,

department.location

from employee, department

Where the employee.id = department.id;

Id NameDeptnameLocation
1SonamHRSalt lake
2RishiFinance Dum dum
3RajuOperationsUltadanga
4PriyankaMarketingKalyani

Inserting into views

The syntax should be read as

Insert into view_name(column1, column2, column3…n) values(value1, value2, value3,….n)

To view Emplyee_vw a row needs to be inserted to the statement like

Insert into employee-Vw (name, age, salary,) values( ‘Mahim’, ‘24’, ‘24000’)

The table should look like these after insertion:

NameAgeSalary
Sonam2522000
Rishi2623000
Raju2625000
Priyanka2723500
Mahim2424000

Deleting Views

The syntax for deleting view is:

Delete from view_name Where [Condition]

Delete row from view:

Delete from employee_vw where name = ‘Rishi’;

After deletion the result is displayed thus:

Select * from employee-WV

Sonam2522000
Raju2625000
Priyanka2723500
Mahim2424000

Materialized Views

SQL doesn’t provide any standard definition of materialized views, but it stands for view expressions stored in the database systems. View maintenance is employed to keep the database up to date. This is a useful tool to access the views frequently and saves calculation time.

SQL views add extra security protection to the database, which is extremely important to maintain relational database systems. Pictures can become challenging to use if there are frequent changes to the database structure. So, views are quite handy for creating structures but depend upon the usage.

Related Blogs

  1. SQL Joins
  2. Schema in SQL
  3. Decode in SQL
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