Understanding SQL Views and How to Create Them

SQL views are a powerful tool for organizing and presenting data in a database. They act as virtual tables that combine and modify the data in base tables. This article will discuss the basics of views in SQL, how to create them, and the different types of views available.

Introduction to SQL Views

A view in SQL is a virtual table derived from one or more actual tables. Views do not store data themselves; they merely provide a logical representation of data from one or more tables. You can use views to present a simplified version of data, filter data, or combine data from multiple tables into a single view.

Creating SQL Views

The syntax for creating a view in SQL (specifically in MySQL, as an example) is:

CREATE VIEW [db_name.]view_name [column_list] AS
SELECT [columns]
FROM table
[WHERE conditions]

This allows you to create a view that can be queried like a normal table, but with the added benefits of data filtering and organization.

Basic Syntax for Creating a View in MySQL

CREATE VIEW [db_name.]view_name [column_list]
AS
SELECT [columns]
FROM table
[WHERE conditions]

Here, db_name is the name of the database where the view will be created; view_name is the unique name of the view; and column_list is the list of columns you want to include in the view, which can be specified in parentheses.

Creating Views Using dbForge Studio Query Builder

Alternatively, you can create views using the dbForge Studio Query Builder. This tool simplifies the process by allowing you to drag-and-drop items onto the diagram to generate SQL code for creating views.

Types of SQL Views

There are several types of SQL views, each serving a different purpose:

Simple View

A simple view is created using a single SELECT query that refers to a single table. The syntax for creating a simple view is:

CREATE VIEW Simple_view AS
SELECT columns
FROM table

Example: Creating a simple view in MySQL

CREATE VIEW Simple_view AS
SELECT * FROM BANK_CUSTOMER

Complex View

A complex view is created using one or more SELECT queries that involve joins or aggregations across multiple tables. The syntax is similar to a simple view, but with more complex query logic:

CREATE VIEW Complex_view AS
SELECT _id, _account
FROM Bank_customer bc JOIN Bank_Account ba
ON bc._id  ba._id
WHERE   300000

Example: Creating a complex view in MySQL

CREATE VIEW Complex_view AS
SELECT _id, _account
FROM Bank_customer bc JOIN Bank_Account ba
ON bc._id  ba._id
WHERE   300000

Inline View (Subquery in SELECT Clause)

An inline view is a subquery that is embedded in the FROM clause of a SELECT query. Inline views are useful when you need to filter or aggregate data in a subquery and then use the result in the main query. Here’s an example:

SELECT * FROM (
SELECT _id, _account
FROM Bank_customer bc JOIN Bank_Account ba
ON bc._id  ba._id
WHERE   300000
) subquery

Materialized View (Physical View)

A materialized view is a physical copy of the data in a query result. This can be used to improve query performance by precalculating and storing the result of a query. The syntax for creating a materialized view is:

CREATE MATERIALIZED VIEW [db_name.]mat_view_name [column_list]
AS
SELECT [columns]
FROM table
[WHERE conditions]

The materialized view is stored as a physically created table, unlike regular views, which are not stored and are not visible in the database.

Conclusion

SQL views are a valuable tool for organizing, presenting, and filtering data in SQL databases. They can be created using simple or complex queries and come in various types, each suitable for different purposes. Understanding how to create and use views can significantly enhance your database management skills.

Keywords

SQL views, creating views, types of views