Sqlite3 Do I have to attach a database on every connection? - sqlite

Question

The following piece of code creates two databases:
import sqlite3
db = 'brazil'
conn = sqlite3.connect(db+'.db')
c = conn.cursor()
qCreate = """
CREATE TABLE states
(zip_id numeric NOT NULL,
state_name text NOT NULL,
CONSTRAINT pk_brazil
PRIMARY KEY (zip_id) """
c.execute(qCreate)
conn.commit()
conn.close()
db = 'city'
conn = sqlite3.connect(db+'.db')
c = conn.cursor()
qCreate = """CREATE TABLE rio_de_janeiro
(zip_id numeric NOT NULL,
beach_name text NOT NULL,
CONSTRAINT pk_rio
PRIMARY KEY (zip_id)
"""
c.execute(qCreate)
conn.commit()
conn.close()
The following piece of code attaches the database RIO to the database BRAZIL and prints all the databases (Rio and Brazil).
db = 'brazil'
conn = sqlite3.connect(db+'.db')
c = conn.cursor()
qCreate = """ATTACH DATABASE ? AS competition """
c.execute(qCreate, ('rio.db',))
c.execute("PRAGMA database_list")
data = c.fetchall()
print data
conn.commit()
conn.close()
However the following piece of code prints only Brazil database:
db = 'brazil'
conn = sqlite3.connect(db+'.db')
c = conn.cursor()
c.execute("PRAGMA database_list")
data = c.fetchall()
print data
conn.commit()
conn.close()
The attached database is no longer attached.
The sqlite3 documentation hints on these lines:
The ATTACH DATABASE statement adds another database file to the current database connection.
Do I have to attach the database every time?
I planed to use attached databases for schemas, but maybe I should try something else?
I am using python in Pythonista App in iOS

Answer 1

Almost all settings you can change in SQLite apply only to the current connection, i.e., are not saved in the database file.
So you have to re-ATTACH any databases whenever you have re-opened the main database.
Using attached databases makes sense only if you must use multiple database files due to some external constraint. In most cases, you should use only a single database.
SQLite does not have schemas. If you want to emulate them with attached databases, you have to live with the limitations of that approach.