# ClickHouse® tips #6: Filtering data in subqueries to avoid joins

DevFeed: [ClickHouse® tips #6: Filtering data in subqueries to avoid joins](<https://devfeed.tech/articles/clickhouse-tips-6-filtering-data-in-subqueries-to-avoid-joins-18723.md>)

Original publisher: [Read original article](<https://www.tinybird.co/blog/tips-6-faster-joins-without-joining-using-where>)

Author: Xoel López

Published: 2021-04-23T00:00:00Z

Content type: tutorial

Language: en

Sources: [Tinybird](<https://devfeed.tech/sources/tinybird.md>)

Topics: [clickhouse](<https://devfeed.tech/topics/clickhouse.md>), [data](<https://devfeed.tech/topics/data.md>)

Tags: [clickhouse](<https://devfeed.tech/tags/clickhouse.md>), [data](<https://devfeed.tech/tags/data.md>), [the-data-base](<https://devfeed.tech/tags/the-data-base.md>), [tips](<https://devfeed.tech/tags/tips.md>)

## AI overview

A ClickHouse query optimization tip explains that filtering data in subqueries with WHERE can avoid full joins when joins are not actually needed, potentially making those queries faster.

## Source excerpt

Faster JOINs without joining: use WHERE instead. This ClickHouse tip speeds up queries that don't actually need full joins.