This is incorrect and has been for several versions of the CLI. What do you mean when you say SQLite? are you referring to the sqlite command line program? If yes, then no What you think of as 'the database' being 'opened' is really a 'connection' being created and the 'main' database being attached to that connection. It ATTACHes a new database file to an existing connection, thus now allowing the connection to get from here (you and your application) to there (the database which was opened when the connection was opened) and to the new database which you attached with a specified name. The SQL ATTACH command, however, does exactly what it says on the tin. Nonetheless, *sqlite3_open* creates an sqlite3 connection and, as a side effect, opens a database file (of some description) for the 'other end' of the connection - a connection from here to there would be completely useless if it had only a here and no there - would not it be? This database may be a 'file' or it may be ':memory:', or it may be something else. This connection is required to have (at least) a single database file attached to it, called 'main' (or other name specified by your local copy/application sqlite3 library). Sqlite3_open* API's open a database connection. When you attach another database, you can assign what you want this schema name to be. The original one is identified as main.table1, and the one in fred is fred.table1. If you attached another database called 'fred' which also had table1 in it, you'd have to tell sqlite which table1 you wanted - the original one, or the one in fred. Lets assume it has a table called 'table1' in it. When you normally open a database file, it gets opened in a schema called 'main'. It is far easier to work on a database file rather than have to rely on attaching other databases though, as it's not always clear what 'other databases' you may need. Or, if a database gets large, you can split it into smaller chunks, with each chunk containing one or more tables.

This is handy if you want to query data across two different databases. 'Attach' is used to add another database file to the existing database. 'Open' is generally used to open one particular database file.

Sqlite command line attach adatabase