---
title: "Table Joins"
slug: "table-joins"
updated: 2022-07-06T08:58:36Z
published: 2022-07-06T08:58:36Z
canonical: "docs.preset.io/table-joins"
---

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

# Table Joins

## Overview

When writing query joins in SQL lab, there are several restrictions:

1. Joined tables must be from the same database.
2. Joined tables can be from different schemas within a database.
3. Joined tables can be from the same schema within a database.

---

## Examples

### Example for Restriction 1

There exists a table called **public.example_one** in a Postgresql database called **post** and another table called **public.example_two** in an Athena database called **ath**.

A SQL query such as:

```
SELECT * FROM post.public.example_one 
JOIN ath.public.example_two ON example_one.id = example_two.id
```

...will be invalid. Even if the two databases were both Postgresql databases, you will not be able to join. Tables **must** originate from the same database.

### Example for Restriction 2

There exists a table called **schema_one.example_one** and another table called **schema_two.example_two** in the same database.

A SQL query such as:

```
SELECT * FROM schema_one.example_one
JOIN schema_two.example_two ON example_one.id = example_two.id
```

...will be valid.

### Example for Restriction 3

There exists a table called **public.example_one** and another table called **public.example_two** in the same database.

A SQL query such as:

```
SELECT * FROM public.example_one
JOIN public.example_two ON example_one.id = example_two.id
```

...will be valid.

          

#### Specify the database you are using in SQL Lab

          

From the [SQL Editor](/v1/docs/querying-and-analysis), in the **Database** field, ensure that you specify the database that contains your tables/schemas.

![Screen Shot 2021-08-15 at 10.48.37 PM.png](https://cdn.document360.io/4749ddf8-aa05-4f3f-80e1-07a5d2d0f137/Images/Documentation/Screen%20Shot%202021-08-15%20at%2010.48.37%20PM.png)