Benefits of Using Views in sql
In SQL database management systems, views are virtual database user-created table views that help database users interact with table data in an easier or customized order. Table views are created by running a SELECT command or statement query, and these table views are used like tables in other SQL statements. Remember, user-created table views do not store the data themselves; instead, they store and process the table query used to generate the data. When a database user runs a query against a table view, the system runs the underlying SELECT query to retrieve the data stored in the database.
Some advantages of creating views in an SQL database.
Easy and fast access to database table data.
Abstraction of complexity – User-created table views abstract the underlying table structure, making it easier to create complex table queries. Database users can interact directly with a table view that displays a simpler or more logical table structure according to conditions or logic defined by the database user, instead of having to create and run complex joins or subqueries multiple times.
Example of creating a view instead of repeatedly creating a complex query to join multiple tables in a database.
CREATE VIEW Employee_Info AS
SELECT e.employee_id, e.emp_name, d.department_name, e.salary
FROM employee e
JOIN department d ON e.department_id = d.department_id;
Data simplification – User-created table views can display specific columns of a table, or join and group multiple database tables into a single virtual table. This is helpful in situations where the database user only needs a subset of the table data, or needs to display it in a specific table format.
Enhanced security for sensitive database data.
Limiting Access to Sensitive Data – Database table views help control how database users can access data. Instead of providing users with direct access to the base or root tables, users can create views that display only a particular table column or table row, thus securing confidential database table data (such as employee ID, email, salary, social security number, etc.).
A database user can create a view that omits confidential columns from the database table.
For example.
CREATE VIEW EmployeeDetails AS
SELECT employee_id, emp_name, department_name
FROM employee
JOIN department ON employee.department_id = department.department_id;
This view created on the employee and department tables omits confidential table data such as salary or personal identification numbers.
Data Masking – Views in database tables can also be used for data masking, where confidential or detailed table data is hidden or replaced with more general information or data. For example, masking employee salary data.
Improved Database Table Query Performance (in some cases).
Predefined Queries – Database table views can help optimize frequently used table queries by defining them once and using them multiple times, saving time and effort for database users and applications. While table views themselves don’t inherently improve performance, using table views that encapsulate complex joins or calculations in the database table reduces the complexity of table queries run multiple times, making it easier for database developers or users to efficiently retrieve table data using the table view.
Materialized Views (in some databases) – Some database software, such as PostgreSQL and Oracle, support materialized table views, which are stored on secondary disk storage and automatically refreshed periodically. These table views allow users to pre-compute and cache query results, improving query performance for frequently accessed table data.
Example – A materialized view in a database table can store aggregated table data and be updated at regular intervals, avoiding the need to calculate the data multiple times every time the table view query is run.
Centralized business logic in database tables.
Encapsulation of Logic – Complex business logic can be centralized and managed in database table views. Instead of inserting or embedding complex logic in every user application or query, database users can define it in a view, and database users can then run that view query to obtain the table view results.
Example – Here, a view in the database table might include complex logic to calculate the total cost of a customer order, including product taxes and discounts, so that the application doesn’t need to apply this logic multiple times.
CREATE VIEW OrderReport AS
SELECT order_id, customer_id, total_price + (total_price * 0.10) AS total_with_tax
FROM orders;
Consistency – Remember, database table views encapsulate and preview business rules, which helps us ensure that the same logic is consistently applied across different applications or users.
Data Independence Features.
Separation of Logical and Physical Models – Database table views provide a layer of data abstraction between the table and its logical representation in the physical storage format of the data. Modifications to the underlying database schema, such as modifying the name of an existing table or adding new table columns, can be isolated from database users by adjusting the table view definition.
Example – If a database user needs to modify the name of a column in a table, the table view is updated to display the new table view column name without requiring modifications to queries or applications that depend on the table view.
Schema Evolution – User-created table views allow for the evolution of database table schemas without breaking existing applications, making database table view storage, retrieval, and maintenance easier, and significantly reducing the risk of database view downtime or application failure.
Data View Reusability and Maintenance.
Reusing Common Queries – Database table views allow database users to define complex queries once and reuse them across multiple applications or users. This reduces source code redundancy in SQL, making it easier to maintain and update.
Easier Maintenance – If a database user needs to modify business logic or a query, they only need to update the view instead of updating every instance of the query in their applications or scripts. This ensures that table view modifications are consistently applied to all users or applications that depend on the view.
Database Data Aggregation and Reporting.
Aggregation – Database table views are often used to apply data aggregation functions, such as calculating sums, averages, and other functions. Instead of creating multiple data view aggregation queries in the database, database users can define a single table view to manage this.
Example – A user-created table view can provide a summary of sales data by year, allowing database users to quickly access and preview total sales for each year.
CREATE VIEW OneYear_Sales AS
SELECT YEAR(order_date) AS year, SUM(order_total) AS total_sales
FROM orders
GROUP BY YEAR(order_date);
Simplifying Reporting – Table views provide a simple method for database users to create reports that aggregate data from different tables separately. Database users can query the view for reporting without needing to know the underlying table structure or SQL syntax.
