ClickHouse/docs/en/sql-reference/dictionaries/index.md

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slug: /en/sql-reference/dictionaries/
sidebar_label: Dictionaries
sidebar_position: 35
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# Dictionaries

A dictionary is a mapping (`key -> attributes`) that is convenient for various types of reference lists.

ClickHouse supports special functions for working with dictionaries that can be used in queries. It is easier and more efficient to use dictionaries with functions than a `JOIN` with reference tables.

ClickHouse supports:

-   [Built-in dictionaries](../../sql-reference/dictionaries/internal-dicts.md#internal_dicts) with a specific [set of functions](../../sql-reference/functions/ym-dict-functions.md).
-   [Plug-in (external) dictionaries](../../sql-reference/dictionaries/external-dictionaries/external-dicts.md#dicts-external-dicts) with a [set of functions](../../sql-reference/functions/ext-dict-functions.md).
Get rid of toc_en.yml (#10023) 2020-04-03 13:23:32 +00:00			`---`
add slugs 2022-08-28 14:53:34 +00:00			`slug: /en/sql-reference/dictionaries/`
Removed /ja folder, cleaned up /ru markdown 2022-04-09 13:29:05 +00:00			`sidebar_label: Dictionaries`
			`sidebar_position: 35`
Get rid of toc_en.yml (#10023) 2020-04-03 13:23:32 +00:00			`---`

Remove H1 anchor tags from docs 2022-06-02 10:55:18 +00:00			`# Dictionaries`
Sources for english documentation switched to Markdown. Edit page link is fixed too for both language versions of documentation. 2017-12-28 15:13:23 +00:00
Update of english documentation (#2918) * Updating of english translation. * Some bugs are fixed. 2018-09-04 11:18:59 +00:00			A dictionary is a mapping (`key -> attributes`) that is convenient for various types of reference lists.
Sources for english documentation switched to Markdown. Edit page link is fixed too for both language versions of documentation. 2017-12-28 15:13:23 +00:00
Update of english documentation (#2918) * Updating of english translation. * Some bugs are fixed. 2018-09-04 11:18:59 +00:00			ClickHouse supports special functions for working with dictionaries that can be used in queries. It is easier and more efficient to use dictionaries with functions than a `JOIN` with reference tables.

			`ClickHouse supports:`

[docs] split aggregate function and system table references (#11742) * prefer relative links from root * wip * split aggregate function reference * split system tables 2020-06-18 08:24:31 +00:00			`- [Built-in dictionaries](../../sql-reference/dictionaries/internal-dicts.md#internal_dicts) with a specific [set of functions](../../sql-reference/functions/ym-dict-functions.md).`
			`- [Plug-in (external) dictionaries](../../sql-reference/dictionaries/external-dictionaries/external-dicts.md#dicts-external-dicts) with a [set of functions](../../sql-reference/functions/ext-dict-functions.md).`
Sources for english documentation switched to Markdown. Edit page link is fixed too for both language versions of documentation. 2017-12-28 15:13:23 +00:00