---
title: "Understanding FROM in PostgreSQL (With Examples)"
description: "The FROM clause in PostgreSQL is used to specify the table from which to select or delete data. Learn how to use it with practical examples."
section: "Postgres basics"
---
> **TimescaleDB is now Tiger Data.**
*Written by Team Timescale*
**
In PostgreSQL or TimescaleDB, the `FROM` clause is fundamental to querying data. It specifies the PostgreSQL table from which to retrieve or delete data, serving as the starting point for your queries. It is a critical part of any `SELECT`, `DELETE`, or `UPDATE` statement.
The `FROM` clause can also be used to join multiple tables, allowing you to combine data from different sources.
## PostgreSQL FROM Syntax
The basic syntax of the `FROM` clause is as follows:
`SELECT column1, column2, ...
FROM table_name;
`When joining multiple tables, the syntax is:
`SELECT column1, column2, ...
FROM table1
JOIN table2 ON table1.column = table2.column;
`
### Example table
Let's consider a table `iot_data` with the following structure and data:
`CREATE TABLE iot_data (
id SERIAL PRIMARY KEY,
device_id VARCHAR(50),
temperature NUMERIC,
humidity NUMERIC,
recorded_at TIMESTAMP
);`
`INSERT INTO iot_data (device_id, temperature, humidity, recorded_at) VALUES
('device_1', 22.5, 55.0, '2023-01-15 08:00:00'),
('device_2', 21.0, 60.0, '2023-01-15 08:05:00'),
('device_1', 23.0, 57.0, '2023-01-15 08:10:00'),
('device_2', 19.5, 62.0, '2023-01-15 08:15:00'),
('device_1', 20.0, 59.0, '2023-01-15 08:20:00'),
('device_3', 24.0, 54.0, '2023-01-15 08:25:00'),
('device_2', 18.5, 63.0, '2023-01-15 08:30:00'),
('device_3', 22.0, 55.5, '2023-01-15 08:35:00'),
('device_1', 21.5, 58.0, '2023-01-15 08:40:00'),
('device_3', 23.5, 53.0, '2023-01-15 08:45:00');`
``
### Practical examples
Let's dive into some examples to see the `FROM` clause in action.
**
Example 1: Selecting data from a single table**
Suppose we want to retrieve all the data from the `iot_data` table. We can use the `FROM` clause to achieve this:
`SELECT id, device_id, temperature, humidity, recorded_at
FROM iot_data;
`**Result:**
`id | device_id | temperature | humidity | recorded_at
----+-----------+-------------+----------+---------------------
1 | device_1 | 22.5 | 55.0 | 2023-01-15 08:00:00
2 | device_2 | 21.0 | 60.0 | 2023-01-15 08:05:00
3 | device_1 | 23.0 | 57.0 | 2023-01-15 08:10:00
4 | device_2 | 19.5 | 62.0 | 2023-01-15 08:15:00
5 | device_1 | 20.0 | 59.0 | 2023-01-15 08:20:00
6 | device_3 | 24.0 | 54.0 | 2023-01-15 08:25:00
7 | device_2 | 18.5 | 63.0 | 2023-01-15 08:30:00
8 | device_3 | 22.0 | 55.5 | 2023-01-15 08:35:00
9 | device_1 | 21.5 | 58.0 | 2023-01-15 08:40:00
10 | device_3 | 23.5 | 53.0 | 2023-01-15 08:45:00
`
This query retrieves all columns from the `iot_data `table.
**Example 2: Filtering data with WHERE **
To retrieve data for a specific device, we can combine the `FROM` clause with a [WHERE clause](#):
`SELECT id, device_id, temperature, humidity, recorded_at
FROM iot_data
WHERE device_id = 'device_1';
`**Result:**
**
**`id | device_id | temperature | humidity | recorded_at
----+-----------+-------------+----------+---------------------
1 | device_1 | 22.5 | 55.0 | 2023-01-15 08:00:00
3 | device_1 | 23.0 | 57.0 | 2023-01-15 08:10:00
5 | device_1 | 20.0 | 59.0 | 2023-01-15 08:20:00
9 | device_1 | 21.5 | 58.0 | 2023-01-15 08:40:00
`
This query retrieves rows where the `device_id` is 'device_1'.
****
**Example 3: Joining multiple tables**
Suppose we have another table `device_info` that contains additional information about the devices:
`CREATE TABLE device_info (
device_id VARCHAR(50) PRIMARY KEY,
device_name VARCHAR(100),
location VARCHAR(100)
);`
`INSERT INTO device_info (device_id, device_name, location) VALUES
('device_1', 'Temperature Sensor 1', 'Building A'),
('device_2', 'Temperature Sensor 2', 'Building B'),
('device_3', 'Temperature Sensor 3', 'Building C');
`
We can join `iot_data` with `device_info` to get the location and name of each device along with their recorded data:
`SELECT iot_data.id, iot_data.device_id, device_info.device_name, device_info.location, iot_data.temperature, iot_data.humidity, iot_data.recorded_at
FROM iot_data
JOIN device_info ON iot_data.device_id = device_info.device_id;
`
**Result:**
`id | device_id | device_name | location | temperature | humidity | recorded_at
----+-----------+--------------------+--------------+-------------+----------+---------------------
1 | device_1 | Temperature Sensor 1 | Building A | 22.5 | 55.0 | 2023-01-15 08:00:00
2 | device_2 | Temperature Sensor 2 | Building B | 21.0 | 60.0 | 2023-01-15 08:05:00
3 | device_1 | Temperature Sensor 1 | Building A | 23.0 | 57.0 | 2023-01-15 08:10:00
4 | device_2 | Temperature Sensor 2 | Building B | 19.5 | 62.0 | 2023-01-15 08:15:00
5 | device_1 | Temperature Sensor 1 | Building A | 20.0 | 59.0 | 2023-01-15 08:20:00
6 | device_3 | Temperature Sensor 3 | Building C | 24.0 | 54.0 | 2023-01-15 08:25:00
7 | device_2 | Temperature Sensor 2 | Building B | 18.5 | 63.0 | 2023-01-15 08:30:00
8 | device_3 | Temperature Sensor 3 | Building C | 22.0 | 55.5 | 2023-01-15 08:35:00
9 | device_1 | Temperature Sensor 1 | Building A | 21.5 | 58.0 | 2023-01-15 08:40:00
10 | device_3 | Temperature Sensor 3 | Building C | 23.5 | 53.0 | 2023-01-15 08:45:00
`
This query retrieves data from both `iot_data` and `device_info` tables, providing a complete picture of each device's data along with its location and name.
## Next Steps
The `FROM` clause is a fundamental part of SQL and PostgreSQL, specifying the source tables for your queries. To learn more about other foundational PostgreSQL concepts, check out our [Postgres basics](https://www.timescale.com/learn/postgres-basics) section. For more advanced guides, visit [Postgres best practices](https://www.timescale.com/learn/postgres-best-practices/).