Clean-up the SQLite introduction.

This commit is contained in:
Raymond Hettinger 2012-04-17 22:48:06 -04:00
parent 0e15a6e244
commit 33c66301ee
1 changed files with 26 additions and 26 deletions

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@ -23,7 +23,7 @@ represents the database. Here the data will be stored in the
:file:`/tmp/example` file::
import sqlite3
conn = sqlite3.connect('/tmp/example')
conn = sqlite3.connect('example.db')
You can also supply the special name ``:memory:`` to create a database in RAM.
@ -33,13 +33,11 @@ and call its :meth:`~Cursor.execute` method to perform SQL commands::
c = conn.cursor()
# Create table
c.execute('''create table stocks
(date text, trans text, symbol text,
qty real, price real)''')
c.execute('''CREATE TABLE stocks
(date text, trans text, symbol text, qty real, price real)''')
# Insert a row of data
c.execute("""insert into stocks
values ('2006-01-05','BUY','RHAT',100,35.14)""")
c.execute("INSERT INTO stocks VALUES ('2006-01-05','BUY','RHAT',100,35.14)")
# Save (commit) the changes
conn.commit()
@ -47,16 +45,17 @@ and call its :meth:`~Cursor.execute` method to perform SQL commands::
# We can also close the cursor if we are done with it
c.close()
Usually your SQL operations will need to use values from Python variables. You
shouldn't assemble your query using Python's string operations because doing so
is insecure; it makes your program vulnerable to an SQL injection attack.
The data you've saved is persistent and is available in subsequent sessions::
import sqlite3
conn = sqlite3.connect('/tmp/example')
conn = sqlite3.connect('example.db')
c = conn.cursor()
Usually your SQL operations will need to use values from Python variables. You
shouldn't assemble your query using Python's string operations because doing so
is insecure; it makes your program vulnerable to an SQL injection attack
(see http://xkcd.com/327/ for humorous example of what can go wrong).
Instead, use the DB-API's parameter substitution. Put ``?`` as a placeholder
wherever you want to use a value, and then provide a tuple of values as the
second argument to the cursor's :meth:`~Cursor.execute` method. (Other database
@ -64,19 +63,20 @@ modules may use a different placeholder, such as ``%s`` or ``:1``.) For
example::
# Never do this -- insecure!
symbol = 'IBM'
c.execute("select * from stocks where symbol = '%s'" % symbol)
symbol = 'RHAT'
c.execute("SELECT * FROM stocks WHERE symbol = '%s'" % symbol)
# Do this instead
t = (symbol,)
c.execute('select * from stocks where symbol=?', t)
c.execute('SELECT * FROM stocks WHERE symbol=?', t)
print c.fetchone()
# Larger example
for t in [('2006-03-28', 'BUY', 'IBM', 1000, 45.00),
('2006-04-05', 'BUY', 'MSFT', 1000, 72.00),
('2006-04-06', 'SELL', 'IBM', 500, 53.00),
]:
c.execute('insert into stocks values (?,?,?,?,?)', t)
# Larger example that inserts many records at a time
purchases = [('2006-03-28', 'BUY', 'IBM', 1000, 45.00),
('2006-04-05', 'BUY', 'MSFT', 1000, 72.00),
('2006-04-06', 'SELL', 'IBM', 500, 53.00),
]
c.executemany('INSERT INTO stocks VALUES (?,?,?,?,?)', purchases)
To retrieve data after executing a SELECT statement, you can either treat the
cursor as an :term:`iterator`, call the cursor's :meth:`~Cursor.fetchone` method to
@ -85,16 +85,13 @@ matching rows.
This example uses the iterator form::
>>> c = conn.cursor()
>>> c.execute('select * from stocks order by price')
>>> for row in c:
... print row
...
>>> for row in c.execute('SELECT * FROM stocks ORDER BY price'):
print row
(u'2006-01-05', u'BUY', u'RHAT', 100, 35.14)
(u'2006-03-28', u'BUY', u'IBM', 1000, 45.0)
(u'2006-04-06', u'SELL', u'IBM', 500, 53.0)
(u'2006-04-05', u'BUY', u'MSFT', 1000, 72.0)
>>>
.. seealso::
@ -107,6 +104,9 @@ This example uses the iterator form::
The SQLite web page; the documentation describes the syntax and the
available data types for the supported SQL dialect.
http://www.w3schools.com/sql/
Tutorial, reference and examples for learning SQL syntax.
:pep:`249` - Database API Specification 2.0
PEP written by Marc-André Lemburg.