SQL Views and Indexes

In this unit, we will delve into two important aspects of SQL: Views and Indexes. Both of these concepts play a crucial role in managing and retrieving data efficiently from a database.

SQL Views

A view in SQL is essentially a virtual table based on the result-set of an SQL statement. It contains rows and columns, just like a real table. The fields in a view are fields from one or more real tables in the database.

Creating SQL View

You can create a view by using the CREATE VIEW statement. The syntax is as follows:

CREATE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
WHERE condition;

The CREATE VIEW statement creates a new view that you can later use just like a regular table. The SELECT statement after the AS keyword is used to define what the view consists of - it can be the columns from one or more tables, and can also include conditions using the WHERE clause.

For example, if you have a table named "Employees" and you want to create a view that only shows the employee's name and their salary, you can do so with the following SQL statement:

CREATE VIEW Employee_Salaries AS
SELECT name, salary
FROM Employees;

SQL Indexes

An index in SQL is used to speed up the retrieval of records from a database. An index is a data structure (most commonly a B- tree) that improves the speed of data retrieval operations on a database table.

Creating SQL Index

You can create an index on a table with the CREATE INDEX statement. The syntax is as follows:

CREATE INDEX index_name
ON table_name (column1, column2, ...);

The CREATE INDEX statement is used to create an index in a table. You need to specify the name of the index, the name of the table, and the name of the column(s) that you want to index.

For example, if you have a table named "Employees" and you want to create an index on the "name" column, you can do so with the following SQL statement:

CREATE INDEX idx_employee_name
ON Employees (name);

In conclusion, views and indexes are powerful tools in SQL that can help you manage and retrieve data more efficiently. Views allow you to create virtual tables based on specific conditions, while indexes speed up data retrieval operations on a database table.