Скачать или смотреть How to Create a View in PostgreSQL

Learn how to effectively create a view in PostgreSQL, especially if you're migrating from SQL Server. This guide simplifies the process and helps you adapt your SQL code for PostgreSQL syntax.
---
This video is based on the question https://stackoverflow.com/q/67717947/ asked by the user 'Bhavin Varsur' ( https://stackoverflow.com/u/8443793/ ) and on the answer https://stackoverflow.com/a/67749854/ provided by the user 'Bhavin Varsur' ( https://stackoverflow.com/u/8443793/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: create view in postgresql

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
How to Create a View in PostgreSQL: A Step-by-Step Guide

Migrating from one database system to another can come with its own set of challenges, especially when it involves different schemas and syntax. One significant step in this journey is creating views that integrate data from multiple tables. This post will explore how to create a view in PostgreSQL, based on a scenario involving migrating from SQL Server.

The Problem

You’ve recently migrated your SQL Server database to PostgreSQL and want to create a view that pulls data from several tables. While crafting the view worked seamlessly in SQL Server, you're facing hurdles in PostgreSQL due to differences in syntax and schema. You might be wondering:

How do you create a view in PostgreSQL?

What should you change in your SQL code from SQL Server to make it work in PostgreSQL?

If you're new to PostgreSQL and unsure about the process, don’t worry! Let’s break it down.

Understanding Views

A view in a database is a virtual table that is based on the result of a SQL query. Views can encapsulate complex joins and calculations, providing a simpler interface to users or applications. They are useful for:

Simplifying data access

Limiting data visibility (security)

Abstracting complex queries

Converting SQL Server View to PostgreSQL

Here’s how you can convert your SQL Server view into a PostgreSQL-compatible version, focusing on the solution step-by-step.

Step 1: Create the View Syntax

In PostgreSQL, creating or replacing a view is done with the CREATE OR REPLACE VIEW statement. Here's how the general syntax looks like:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Modify the SQL from SQL Server

Let’s take a look at your original SQL Server view code and how to transition it to PostgreSQL.

Original SQL Server Code:

[[See Video to Reveal this Text or Code Snippet]]

Modified PostgreSQL Code:

[[See Video to Reveal this Text or Code Snippet]]

Key Changes Made

Syntax: Instead of using ISNULL, we used COALESCE, which is the equivalent function in PostgreSQL.

Data Type Casting: PostgreSQL requires explicit casting (e.g., (-1)::bigint) for data types.

JOIN Syntax: PostgreSQL supports different JOIN functionalities similar to SQL Server, but ensuring the correct syntax according to PostgreSQL is crucial.

Conclusion

Creating views in PostgreSQL might seem daunting if you're transitioning from SQL Server due to syntax and schema differences. By following the structured approach outlined in this guide, you should be able to adapt your SQL views seamlessly. Always remember to check your SQL functions and adjust them according to PostgreSQL requirements.

Feel free to reach out if you have further questions about PostgreSQL or database migration!