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75 lines
2.3 KiB
Markdown
75 lines
2.3 KiB
Markdown
---
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sidebar_position: 43
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sidebar_label: DETACH
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---
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# DETACH Statement
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Makes the server "forget" about the existence of a table, a materialized view, or a dictionary.
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**Syntax**
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``` sql
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DETACH TABLE|VIEW|DICTIONARY [IF EXISTS] [db.]name [ON CLUSTER cluster] [PERMANENTLY]
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```
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Detaching does not delete the data or metadata of a table, a materialized view or a dictionary. If an entity was not detached `PERMANENTLY`, on the next server launch the server will read the metadata and recall the table/view/dictionary again. If an entity was detached `PERMANENTLY`, there will be no automatic recall.
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Whether a table or a dictionary was detached permanently or not, in both cases you can reattach them using the [ATTACH](../../sql-reference/statements/attach.md) query.
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System log tables can be also attached back (e.g. `query_log`, `text_log`, etc). Other system tables can't be reattached. On the next server launch the server will recall those tables again.
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`ATTACH MATERIALIZED VIEW` does not work with short syntax (without `SELECT`), but you can attach it using the `ATTACH TABLE` query.
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Note that you can not detach permanently the table which is already detached (temporary). But you can attach it back and then detach permanently again.
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Also you can not [DROP](../../sql-reference/statements/drop#drop-table) the detached table, or [CREATE TABLE](../../sql-reference/statements/create/table.md) with the same name as detached permanently, or replace it with the other table with [RENAME TABLE](../../sql-reference/statements/rename.md) query.
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**Example**
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Creating a table:
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Query:
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``` sql
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CREATE TABLE test ENGINE = Log AS SELECT * FROM numbers(10);
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SELECT * FROM test;
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```
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Result:
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``` text
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┌─number─┐
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│ 0 │
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│ 1 │
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│ 2 │
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│ 3 │
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│ 4 │
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│ 5 │
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│ 6 │
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│ 7 │
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│ 8 │
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│ 9 │
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└────────┘
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```
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Detaching the table:
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Query:
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``` sql
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DETACH TABLE test;
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SELECT * FROM test;
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```
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Result:
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``` text
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Received exception from server (version 21.4.1):
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Code: 60. DB::Exception: Received from localhost:9000. DB::Exception: Table default.test does not exist.
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```
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**See Also**
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- [Materialized View](../../sql-reference/statements/create/view.md#materialized)
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- [Dictionaries](../../sql-reference/dictionaries/index.md)
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