mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-15 19:02:04 +00:00
75 lines
2.3 KiB
Markdown
75 lines
2.3 KiB
Markdown
---
|
|
sidebar_position: 43
|
|
sidebar_label: DETACH
|
|
---
|
|
|
|
# DETACH Statement {#detach}
|
|
|
|
Makes the server "forget" about the existence of a table, a materialized view, or a dictionary.
|
|
|
|
**Syntax**
|
|
|
|
``` sql
|
|
DETACH TABLE|VIEW|DICTIONARY [IF EXISTS] [db.]name [ON CLUSTER cluster] [PERMANENTLY]
|
|
```
|
|
|
|
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.
|
|
|
|
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.
|
|
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.
|
|
|
|
`ATTACH MATERIALIZED VIEW` does not work with short syntax (without `SELECT`), but you can attach it using the `ATTACH TABLE` query.
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
**Example**
|
|
|
|
Creating a table:
|
|
|
|
Query:
|
|
|
|
``` sql
|
|
CREATE TABLE test ENGINE = Log AS SELECT * FROM numbers(10);
|
|
SELECT * FROM test;
|
|
```
|
|
|
|
Result:
|
|
|
|
``` text
|
|
┌─number─┐
|
|
│ 0 │
|
|
│ 1 │
|
|
│ 2 │
|
|
│ 3 │
|
|
│ 4 │
|
|
│ 5 │
|
|
│ 6 │
|
|
│ 7 │
|
|
│ 8 │
|
|
│ 9 │
|
|
└────────┘
|
|
```
|
|
|
|
Detaching the table:
|
|
|
|
Query:
|
|
|
|
``` sql
|
|
DETACH TABLE test;
|
|
SELECT * FROM test;
|
|
```
|
|
|
|
Result:
|
|
|
|
``` text
|
|
Received exception from server (version 21.4.1):
|
|
Code: 60. DB::Exception: Received from localhost:9000. DB::Exception: Table default.test does not exist.
|
|
```
|
|
|
|
**See Also**
|
|
|
|
- [Materialized View](../../sql-reference/statements/create/view.md#materialized)
|
|
- [Dictionaries](../../sql-reference/dictionaries/index.md)
|