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* enbaskakova-DOCSUP-652 (#101)
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* Update docs/en/sql_reference/aggregate_functions/combinators.md
Co-Authored-By: BayoNet <da-daos@yandex.ru>
* Update docs/en/sql_reference/aggregate_functions/combinators.md
Co-Authored-By: BayoNet <da-daos@yandex.ru>
* Update docs/en/sql_reference/aggregate_functions/combinators.md
Co-Authored-By: BayoNet <da-daos@yandex.ru>
* Update docs/en/sql_reference/aggregate_functions/combinators.md
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* Update docs/en/sql_reference/aggregate_functions/combinators.md
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* "docs(orNull&orDefault): Functions 'orNull&orDefault' have been edited"
* "docs(orNull&orDefault): Functions 'orNull&orDefault' have been edited"
* "docs(orNull&orDefault): Functions 'orNull&orDefault' have been edited"
Co-authored-by: elenbaskakova <elenbaskakova@yandex-team.ru>
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* Revert "enbaskakova-DOCSUP-652 (#101)" (#107)
This reverts commit 639fee7610.
* CLICKHOUSEDOCS-624: Fixed links. Was 60, became 13.
* CLICKHOUSEDOCS-624: Finished fix links in Enlish version.
* CLICKHOUSEDOCS-624: Fixed RU links
Co-authored-by: elenaspb2019 <47083263+elenaspb2019@users.noreply.github.com>
Co-authored-by: elenbaskakova <elenbaskakova@yandex-team.ru>
Co-authored-by: Sergei Shtykov <bayonet@yandex-team.ru>
21 lines
954 B
Markdown
21 lines
954 B
Markdown
---
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toc_folder_title: Dictionaries
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toc_priority: 35
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toc_title: Introduction
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---
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# Dictionaries {#dictionaries}
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A dictionary is a mapping (`key -> attributes`) that is convenient for various types of reference lists.
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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.
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[NULL](../../sql-reference/syntax.md#null-literal) values can’t be stored in a dictionary.
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ClickHouse supports:
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- [Built-in dictionaries](internal-dicts.md#internal_dicts) with a specific [set of functions](../../sql-reference/functions/ym-dict-functions.md).
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- [Plug-in (external) dictionaries](external-dictionaries/external-dicts.md#dicts-external-dicts) with a [set of functions](../../sql-reference/functions/ext-dict-functions.md).
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[Original article](https://clickhouse.tech/docs/en/query_language/dicts/) <!--hide-->
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