postgresql
  1. postgresql-view
PreviousNext

View - (PostgreSQL Views)

A view is a virtual table that does not contain any data but instead retrieves data from one or more existing tables based on a specific query. In this tutorial, we'll discuss the syntax, example, output, explanation, use, important points, and summary of views in PostgreSQL.

Syntax

CREATE VIEW view_name AS
SELECT column_name
FROM table_name
WHERE condition;
  • view_name: The name of the view that you want to create.
  • column_name: The columns that you want to retrieve from the table.
  • table_name: The name of the table that you want to retrieve data from.
  • condition: The condition that you want to apply to retrieve specific data from the table.

Example

Let's create a view that retrieves data from the "students" table.

CREATE VIEW student_view AS
SELECT first_name, last_name, age
FROM students
WHERE age > 18;

Now let's select data from the "student_view" view.

SELECT * FROM student_view;

Output

| first_name | last_name | age |
|------------|-----------|-----|
| John       | Doe       | 19  |
| Jane       | Smith     | 20  |
| Jack       | Black     | 21  |

Explanation

In the above example, we created a new view called "student_view" that retrieves data from the "students" table. The "student_view" view retrieves three columns from the "students" table: "first_name", "last_name", and "age". We also added a condition to the view so that it only retrieves data where the "age" column is greater than 18.

When we select data from the "student_view" view, it retrieves and displays the data that satisfies the view's condition.

Use

Views are useful in situations where you need to retrieve data from one or more tables often and for a specific purpose. Instead of writing the same query over and over again, you can create a view and retrieve data from it as needed.

Views can also be used to simplify complex queries by breaking them down into smaller, more manageable pieces. This can make it easier to write and maintain your queries.

Important Points

  • Views do not store any data themselves. They simply retrieve data from one or more existing tables based on a specific query.
  • Views can be used like tables in PostgreSQL, as they are treated like regular table objects by the database management system.
  • Views are read-only by default, which means that you cannot insert, update, or delete data from a view.
  • Views can improve query performance by pre-computing and storing the results of complex queries that are frequently executed.

Summary

In this tutorial, we discussed views in PostgreSQL. We covered the syntax, example, output, explanation, use, and important points of views. With this knowledge, you can now create views to retrieve data from one or more tables based on a specific query. Views are a powerful tool for simplifying complex queries and improving query performance.

ExistsJoin
Published on: