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94 lines
2.8 KiB
Markdown
94 lines
2.8 KiB
Markdown
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# Dictionary
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The `Dictionary` engine displays the [dictionary](../../query_language/dicts/external_dicts.md) data as a ClickHouse table.
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As an example, consider a dictionary of `products` with the following configuration:
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```xml
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<dictionaries>
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<dictionary>
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<name>products</name>
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<source>
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<odbc>
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<table>products</table>
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<connection_string>DSN=some-db-server</connection_string>
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</odbc>
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</source>
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<lifetime>
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<min>300</min>
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<max>360</max>
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</lifetime>
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<layout>
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<flat/>
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</layout>
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<structure>
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<id>
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<name>product_id</name>
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</id>
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<attribute>
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<name>title</name>
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<type>String</type>
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<null_value></null_value>
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</attribute>
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</structure>
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</dictionary>
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</dictionaries>
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```
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Query the dictionary data:
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```sql
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SELECT
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name,
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type,
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key,
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attribute.names,
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attribute.types,
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bytes_allocated,
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element_count,
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source
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FROM system.dictionaries
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WHERE name = 'products'
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```
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```text
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┌─name─────┬─type─┬─key────┬─attribute.names─┬─attribute.types─┬─bytes_allocated─┬─element_count─┬─source──────────┐
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│ products │ Flat │ UInt64 │ ['title'] │ ['String'] │ 23065376 │ 175032 │ ODBC: .products │
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└──────────┴──────┴────────┴─────────────────┴─────────────────┴─────────────────┴───────────────┴─────────────────┘
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```
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You can use the [dictGet*](../../query_language/functions/ext_dict_functions.md#ext_dict_functions) function to get the dictionary data in this format.
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This view isn't helpful when you need to get raw data, or when performing a `JOIN` operation. For these cases, you can use the `Dictionary` engine, which displays the dictionary data in a table.
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Syntax:
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```sql
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CREATE TABLE %table_name% (%fields%) engine = Dictionary(%dictionary_name%)`
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```
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Usage example:
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```sql
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create table products (product_id UInt64, title String) Engine = Dictionary(products);
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```
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```
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Ok
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```
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Take a look at what's in the table.
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```sql
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select * from products limit 1;
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```
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```text
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┌────product_id─┬─title───────────┐
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│ 152689 │ Some item │
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└───────────────┴─────────────────┘
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```
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[Original article](https://clickhouse.tech/docs/en/operations/table_engines/dictionary/) <!--hide-->
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