> ## Documentation Index
> Fetch the complete documentation index at: https://docs.turso.tech/llms.txt
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# ATTACH DATABASE

> Attach an additional database file to the current connection

# ATTACH DATABASE

The ATTACH DATABASE statement adds another database file to the current connection under a schema name. Once attached, tables in the external database can be queried alongside tables in the main database.

## Syntax

```sql theme={null}
ATTACH [DATABASE] filename AS schema-name;
```

## Description

ATTACH opens the database file at `filename` and makes its tables accessible through the given `schema-name`. Tables in the attached database are referenced as `schema-name.table-name`.

### Clauses

| Clause        | Description                                                                                                                                    |
| ------------- | ---------------------------------------------------------------------------------------------------------------------------------------------- |
| `DATABASE`    | Optional keyword. Has no effect on behavior.                                                                                                   |
| `filename`    | A string expression that evaluates to the path of the database file to attach. Use `':memory:'` to attach an in-memory database.               |
| `schema-name` | The name used to qualify table references from the attached database. This name must be unique among all attached databases on the connection. |

Every connection has a built-in schema named `main` for its primary database. The names `main` and `temp` are reserved and cannot be used as schema names for attached databases.

<Info>
  This feature is experimental and must be [enabled before use](/sql-reference/experimental-features). Attached databases support both read and write operations (INSERT, UPDATE, DELETE, CREATE TABLE, etc.). The attached database's journal mode must match the main database's journal mode (e.g., both WAL or both MVCC).
</Info>

## Examples

### Attach and Query an External Database

```sql theme={null}
-- Attach another database file
ATTACH DATABASE 'archive.db' AS archive;

-- Query a table in the attached database
SELECT * FROM archive.events WHERE event_date > '2025-01-01';
```

### Cross-Database Queries

```sql theme={null}
ATTACH 'customers.db' AS customers_db;

-- Join tables across the main and attached databases
SELECT o.id, o.total, c.name
FROM main.orders o
JOIN customers_db.customers c ON o.customer_id = c.id;
```

### Attach an In-Memory Database

```sql theme={null}
ATTACH ':memory:' AS scratch;
```

## See Also

* [DETACH DATABASE](/sql-reference/statements/detach-database) for removing an attached database
* [SELECT](/sql-reference/statements/select) for querying tables across databases