SQLite Databases - Attach DB

In SQLite, it is possible to attach one or more databases to the current database connection. This allows you to access tables and other objects from multiple databases using a single SQL statement.

Syntax

The syntax for attaching a database in SQLite is as follows:

ATTACH DATABASE 'database_file_name' AS 'alias_name';

Where database_file_name is the name of the file containing the database to be attached and alias_name is the name to be given to the attached database.

Example

Suppose we have two SQLite databases, database1.db and database2.db, and we want to attach database2.db to database1.db:

-- Attach database2.db to database1.db
ATTACH DATABASE 'database2.db' AS db2;

Output

If the attachment succeeds, there will be no output. If there is an error, SQLite will raise an error message.

Explanation

In the example above, we attach database2.db to database1.db by using the ATTACH DATABASE command with database2.db file name and db2 alias. Once attached, we can access tables and other objects from database2.db using db2.table_name syntax.

Use

Attaching databases can be useful when you need to access data from multiple databases using a single SQL statement. It can also be used to backup or restore data from one database to another.

Important Points

• You cannot attach an in-memory database.
• Detaching a database is done using the following statement: DETACH DATABASE alias_name.
• It is not recommended to attach too many databases as it can affect performance.
• Accessing tables from an attached database can be slower than accessing tables from the current database.

Summary

In this tutorial, we learned about attaching databases in SQLite and how to use it to access objects from multiple databases using a single SQL statement. We saw an example of attaching database2.db to database1.db and how to access tables from the attached database. It is important to use database attachment sparingly and be aware of its impact on performance.