mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-13 19:14:30 +00:00
7170f3c534
* prefer relative links from root * wip * split aggregate function reference * split system tables
1020 B
1020 B
| toc_folder_title | toc_priority | toc_title |
|---|---|---|
| Dictionaries | 35 | Introduction |
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.
NULL values can’t be stored in a dictionary.
ClickHouse supports:
- Built-in dictionaries with a specific set of functions.
- Plug-in (external) dictionaries with a set of functions.