How Can I Join Tables Across Multiple SQLite Databases?

Joining Tables from Different SQLite Databases

Question: How can you join tables from multiple SQLite databases?

Answer:

To join tables from different SQLite databases, you can use the ATTACH keyword. However, this feature must be enabled in your build of SQLite, which is typically the case. Moreover, there is a limit on the number of databases that can be attached, which is determined during compilation and usually defaults to 10.

To attach an additional database file to the current connection, use the following syntax:

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

You can view all connected databases by using the following command:

.databases

After attaching the databases, you can join tables across them like so:

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

Important Note:

The database names "main" and "temp" are reserved for the primary database and temporary data objects. Therefore, they should not be used for attachment.

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