---
title: "View and analyze relationships between data (ER diagram, JOIN analysis)"
slug: "erd-and-join-v1"
updated: 2024-09-10T11:26:43Z
published: 2024-09-10T11:26:43Z
canonical: "documents.trocco.io/erd-and-join-v1"
---

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

# View and analyze relationships between data (ER diagram, JOIN analysis)

## summary

TROCCO's Data Catalog allows you to view **ER diagrams** between specified tables. It also supports **JOIN analysis, which** allows you to visually check the relationship between two tables.

              Conditions for tables that allow JOIN analysis

              

JOIN analysis can only be performed between tables with [Column Setting references](/docs/column-reference-v1). For information on how to define a column reference, see [Manual Column Setting](/docs/table-information-v1#%E3%82%AB%E3%83%A9%E3%83%A0%E5%8F%82%E7%85%A7%E3%81%AE%E6%89%8B%E5%8B%95%E5%AE%9A%E7%BE%A9).

              Automatic Column Setting

              

Tables transferred to the data store using a specific Data Source Connector in TROCCO will automatically have Column Settings defined. For more information, see [Connectors Subject to Automatic Column Setting](/docs/automatic-metadata-fetched-v1#%E3%82%AB%E3%83%A9%E3%83%A0%E5%8F%82%E7%85%A7%E3%81%AE%E8%87%AA%E5%8B%95%E5%AE%9A%E7%BE%A9%E3%81%AE%E5%AF%BE%E8%B1%A1%E3%81%A8%E3%81%AA%E3%82%8B%E3%82%B3%E3%83%8D%E3%82%AF%E3%82%BF).

## ER diagram

It is displayed by clicking on the **ER Diagram** tab and selecting the table from **the Display Tables filter**.

![image](https://cdn.document360.io/3a3bae1e-f157-487f-8798-01e9d820e760/Images/Documentation/erd-and-join-v1-2024-08-29-8-19-0.png)

Mouse over a table to highlight the line to the related table.

![image](https://cdn.document360.io/3a3bae1e-f157-487f-8798-01e9d820e760/Images/Documentation/erd-and-join-v1-2024-08-29-8-19-1.png)

### How to display JOIN analysis

Mouse over the midpoint of the line connecting the tables to see the JOIN key. Click on the midpoint as it is, and the **JOIN analysis** will be displayed.

![image](https://cdn.document360.io/3a3bae1e-f157-487f-8798-01e9d820e760/Images/Documentation/erd-and-join-v1-2024-08-29-8-19-2.png)

## JOIN Analysis

JOIN analysis allows you to check the information you want to see when joining two tables, such as the JOIN key, number of uniques, and number of nulls. The number of rows generated when joining two tables can also be visually confirmed by a Venn diagram. Click on **View JOIN Analysis** to perform the analysis.

![image](https://cdn.document360.io/3a3bae1e-f157-487f-8798-01e9d820e760/Images/Documentation/erd-and-join-v1-2024-08-29-8-19-3.png)

You can also choose any table join type in **the JOIN preview** to see a preview of the joined tables. A query for table joins is also displayed. Queries can also be copied by clicking on the icons in the red box below.

![image](https://cdn.document360.io/3a3bae1e-f157-487f-8798-01e9d820e760/Images/Documentation/erd-and-join-v1-2024-08-29-8-19-4.png)