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100 lines
4.8 KiB
Markdown
100 lines
4.8 KiB
Markdown
---
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toc_priority: 38
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toc_title: DICTIONARY
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---
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# CREATE DICTIONARY {#create-dictionary-query}
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Creates a new [external dictionary](../../../sql-reference/dictionaries/external-dictionaries/external-dicts.md) with given [structure](../../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-structure.md), [source](../../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-sources.md), [layout](../../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-layout.md) and [lifetime](../../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-lifetime.md).
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**Syntax**
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``` sql
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CREATE DICTIONARY [OR REPLACE][IF NOT EXISTS] [db.]dictionary_name [ON CLUSTER cluster]
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(
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key1 type1 [DEFAULT|EXPRESSION expr1] [IS_OBJECT_ID],
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key2 type2 [DEFAULT|EXPRESSION expr2],
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attr1 type2 [DEFAULT|EXPRESSION expr3] [HIERARCHICAL|INJECTIVE],
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attr2 type2 [DEFAULT|EXPRESSION expr4] [HIERARCHICAL|INJECTIVE]
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)
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PRIMARY KEY key1, key2
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SOURCE(SOURCE_NAME([param1 value1 ... paramN valueN]))
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LAYOUT(LAYOUT_NAME([param_name param_value]))
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LIFETIME({MIN min_val MAX max_val | max_val})
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SETTINGS(setting_name = setting_value, setting_name = setting_value, ...)
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COMMENT 'Comment'
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```
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External dictionary structure consists of attributes. Dictionary attributes are specified similarly to table columns. The only required attribute property is its type, all other properties may have default values.
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`ON CLUSTER` clause allows creating dictionary on a cluster, see [Distributed DDL](../../../sql-reference/distributed-ddl.md).
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Depending on dictionary [layout](../../../sql-reference/dictionaries/external-dictionaries/external-dicts-dict-layout.md) one or more attributes can be specified as dictionary keys.
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For more information, see [External Dictionaries](../../../sql-reference/dictionaries/external-dictionaries/external-dicts.md) section.
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You can add a comment to the dictionary when you creating it using `COMMENT` clause.
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**Example**
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Input table `source_table`:
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``` text
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┌─id─┬─value──┐
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│ 1 │ First │
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│ 2 │ Second │
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└────┴────────┘
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```
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Creating the dictionary:
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``` sql
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CREATE DICTIONARY dictionary_with_comment
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(
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id UInt64,
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value String
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)
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PRIMARY KEY id
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SOURCE(CLICKHOUSE(HOST 'localhost' PORT tcpPort() TABLE 'source_table'))
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LAYOUT(FLAT())
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LIFETIME(MIN 0 MAX 1000)
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COMMENT 'The temporary dictionary';
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```
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Output the dictionary:
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``` sql
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SHOW CREATE DICTIONARY dictionary_with_comment;
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```
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```text
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┌─statement───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
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│ CREATE DICTIONARY default.dictionary_with_comment
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(
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`id` UInt64,
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`value` String
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)
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PRIMARY KEY id
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SOURCE(CLICKHOUSE(HOST 'localhost' PORT tcpPort() TABLE 'source_table'))
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LIFETIME(MIN 0 MAX 1000)
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LAYOUT(FLAT())
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COMMENT 'The temporary dictionary' │
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└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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```
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Output the comment to dictionary:
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``` sql
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SELECT comment FROM system.dictionaries WHERE name == 'dictionary_with_comment' AND database == currentDatabase();
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```
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```text
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┌─comment──────────────────┐
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│ The temporary dictionary │
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└──────────────────────────┘
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```
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**See Also**
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- [system.dictionaries](../../../operations/system-tables/dictionaries.md) — This table contains information about [external dictionaries](../../../sql-reference/dictionaries/external-dictionaries/external-dicts.md).
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