Strange sqlite3 library behavior

[Victor Lin]

Now I am now developing a program that base on sqlite3 in python.
But there is a strange problem.
That is, all data I insert into sqlite database do not goes into file
in disk.
It is really strange....
Why do these data just keep in memory and discarded?

All things that really store in file is the table.
If I create a table, it would appears in the sqlite file.

This is the example :

import sqlite3

createSyntax = """CREATE TABLE IF NOT EXISTS category(
                    id INTEGER NOT NULL PRIMARY KEY
                )"""

createSyntax2 = """CREATE TABLE IF NOT EXISTS category2(
                    id INTEGER NOT NULL PRIMARY KEY
                )"""

insertSyntax = """INSERT INTO category VALUES (1234)"""

db = sqlite3.connect('test.db')
cur = db.cursor()
cur.execute(createSyntax)
cur.execute(insertSyntax)
# only by doing so can let inserted data store in file
cur.execute(createSyntax2)
cur.execute('select * from category')
print cur.fetchall()

db.close()

raw_input()


After I tried some way. I found that create table force data goes into
file. Otherwise all data would just keep in memory and discarded with
the program's ending.
Why sqlite3 just keep inserted data in memory? And how to force
inserted data into file?

Thanks.

Victor Lin.