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59 lines
2.0 KiB
Markdown
59 lines
2.0 KiB
Markdown
---
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toc_priority: 40
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toc_title: ATTACH
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---
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# ATTACH Statement {#attach}
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Attaches the table, for example, when moving a database to another server.
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The query does not create data on the disk, but assumes that data is already in the appropriate places, and just adds information about the table to the server. After executing an `ATTACH` query, the server will know about the existence of the table.
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If the table was previously detached ([DETACH](../../sql-reference/statements/detach.md)) query, meaning that its structure is known, you can use shorthand without defining the structure.
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## Syntax Forms {#syntax-forms}
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### Attach Existing Table {#attach-existing-table}
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``` sql
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ATTACH TABLE [IF NOT EXISTS] [db.]name [ON CLUSTER cluster]
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```
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This query is used when starting the server. The server stores table metadata as files with `ATTACH` queries, which it simply runs at launch (with the exception of some system tables, which are explicitly created on the server).
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If the table was detached permanently, it won't be reattached at the server start, so you need to use `ATTACH` query explicitly.
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### Сreate New Table And Attach Data {#create-new-table-and-attach-data}
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**With specify path to table data**
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```sql
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ATTACH TABLE name FROM 'path/to/data/' (col1 Type1, ...)
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```
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It creates new table with provided structure and attaches table data from provided directory in `user_files`.
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**Example**
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Query:
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```sql
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DROP TABLE IF EXISTS test;
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INSERT INTO TABLE FUNCTION file('01188_attach/test/data.TSV', 'TSV', 's String, n UInt8') VALUES ('test', 42);
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ATTACH TABLE test FROM '01188_attach/test' (s String, n UInt8) ENGINE = File(TSV);
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SELECT * FROM test;
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```
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Result:
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```sql
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┌─s────┬──n─┐
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│ test │ 42 │
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└──────┴────┘
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```
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**With specify table UUID** (Only for `Atomic` database)
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```sql
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ATTACH TABLE name UUID '<uuid>' (col1 Type1, ...)
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```
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It creates new table with provided structure and attaches data from table with the specified UUID. |