How Can I Combine Data from Multiple SQLite Databases Using Database Attachment?

Combining Data from Multiple Databases in SQLite: A Step-by-Step Guide

Cross-database table joins can enhance the flexibility and functionality of applications that utilize SQLite databases. Here's a walkthrough of how to achieve this:

Method: Database Attachment

Ensure that your SQLite build allows ATTACH by verifying that it is enabled (it typically is). This allows you to attach an additional database file to your current connection. The maximum number of attachments is determined by the compile-time setting SQLITE_MAX_ATTACHED, which often defaults to 10.

Database Attachment Syntax:

attach 'database1.db' as db1;
attach 'database2.db' as db2;

Querying Attached Databases:

Use the following syntax to query data from attached databases:

select
  *
from
  db1.SomeTable a
    inner join 
  db2.SomeTable b on b.SomeColumn = a.SomeColumn;

Additional Notes:

• Two reserved database names, 'main' and 'temp,' exist for the primary database and for temporary data, respectively. Avoid using these names for database attachments.
• To view all connected databases, use the '.databases' keyword.

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