---
title: "Virtual catalog columns"
slug: "relnote-12-virtual-catalog-columns"
updated: 2023-02-03T17:49:42Z
published: 2023-02-03T17:49:42Z
canonical: "docs.akridata.ai/relnote-12-virtual-catalog-columns"
---

> ## Documentation Index
> Fetch the complete documentation index at: https://docs.akridata.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Virtual catalog columns

Data Explorer has [catalog views](/data-explorer/docs/catalog-views) feature that allows 2 or more catalog tables to be joined together to create a virtual view. The virtual catalog columns extend the [catalog views](/data-explorer/docs/catalog-views) feature by supporting two new capabilities.

1. Ability to add a virtual column to the view that has its contents computed when the query is executed. For e.g., suppose a 2D bounding box is represented by 4 columns(x_left, y_top, x_right, y_bottom) in a catalog table. A virtual column to compute the area of this bounding box can be defined during view creation. On executing the query, the virtual column gets computed from the contents in the 4 columns.
2. Ability to add a virtual column as a type mapping of an existing column. For e.g., suppose catalog table has a column of type double that actually holds prediction confidence from an inference model. Defining a type mapping column allows Data Explorer to
  1. validate that the values of the column are between [0,1].
  2. provide richer functionality, like attaching a confidence score to a bounding box.

![](https://cdn.document360.io/3e9d4528-fbc6-4948-a804-8ee7068e7ac3/Images/Documentation/virtual-columns.png)

![](https://cdn.document360.io/3e9d4528-fbc6-4948-a804-8ee7068e7ac3/Images/Documentation/Screenshot%20from%202023-02-03%2018-59-10.png)