ClickHouse/docs/en/dicts/index.md
2018-04-23 09:20:21 +03:00

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# Dictionaries
`A dictionary` is a mapping (key `->` attributes) that can be used in a query as functions.
You can think of this as a more convenient and efficient type of JOIN with dimension tables.
There are built-in (internal) and add-on (external) dictionaries.