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diff --git a/Doc/lib/libsqlite3.tex b/Doc/lib/libsqlite3.tex index 8c80eb6..db15c00 100644 --- a/Doc/lib/libsqlite3.tex +++ b/Doc/lib/libsqlite3.tex @@ -6,6 +6,105 @@ \sectionauthor{Gerhard Häring}{gh@ghaering.de} \versionadded{2.5} +SQLite is a C library that provides a SQL-language database that +stores data in disk files without requiring a separate server process. +pysqlite was written by Gerhard H\"aring and provides a SQL interface +compliant with the DB-API 2.0 specification described by +\pep{249}. This means that it should be possible to write the first +version of your applications using SQLite for data storage. If +switching to a larger database such as PostgreSQL or Oracle is +later necessary, the switch should be relatively easy. + +To use the module, you must first create a \class{Connection} object +that represents the database. Here the data will be stored in the +\file{/tmp/example} file: + +\begin{verbatim} +conn = sqlite3.connect('/tmp/example') +\end{verbatim} + +You can also supply the special name \samp{:memory:} to create +a database in RAM. + +Once you have a \class{Connection}, you can create a \class{Cursor} +object and call its \method{execute()} method to perform SQL commands: + +\begin{verbatim} +c = conn.cursor() + +# Create table +c.execute('''create table stocks +(date timestamp, trans varchar, symbol varchar, + qty decimal, price decimal)''') + +# Insert a row of data +c.execute("""insert into stocks + values ('2006-01-05','BUY','RHAT',100,35.14)""") +\end{verbatim} + +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. + +Instead, use the DB-API's parameter substitution. Put \samp{?} 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 \method{execute()} +method. (Other database modules may use a different placeholder, +such as \samp{\%s} or \samp{:1}.) For example: + +\begin{verbatim} +# Never do this -- insecure! +symbol = 'IBM' +c.execute("... where symbol = '%s'" % symbol) + +# Do this instead +t = (symbol,) +c.execute('select * from stocks where symbol=?', t) + +# Larger example +for t in (('2006-03-28', 'BUY', 'IBM', 1000, 45.00), + ('2006-04-05', 'BUY', 'MSOFT', 1000, 72.00), + ('2006-04-06', 'SELL', 'IBM', 500, 53.00), + ): + c.execute('insert into stocks values (?,?,?,?,?)', t) +\end{verbatim} + +To retrieve data after executing a SELECT statement, you can either +treat the cursor as an iterator, call the cursor's \method{fetchone()} +method to retrieve a single matching row, +or call \method{fetchall()} to get a list of the matching rows. + +This example uses the iterator form: + +\begin{verbatim} +>>> c = conn.cursor() +>>> c.execute('select * from stocks order by price') +>>> for row in c: +... print row +... +(u'2006-01-05', u'BUY', u'RHAT', 100, 35.140000000000001) +(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'MSOFT', 1000, 72.0) +>>> +\end{verbatim} + +\begin{seealso} + +\seeurl{http://www.pysqlite.org} +{The pysqlite web page.} + +\seeurl{http://www.sqlite.org} +{The SQLite web page; the documentation describes the syntax and the +available data types for the supported SQL dialect.} + +\seepep{249}{Database API Specification 2.0}{PEP written by +Marc-Andr\'e Lemburg.} + +\end{seealso} + + \subsection{Module functions and constants\label{sqlite3-Module-Contents}} \begin{datadesc}{PARSE_DECLTYPES} @@ -467,7 +566,7 @@ connections. If you want \strong{autocommit mode}, then set \member{isolation_level} to None. -Otherwise leave it at it's default, which will result in a plain "BEGIN" +Otherwise leave it at its default, which will result in a plain "BEGIN" statement, or set it to one of SQLite's supported isolation levels: DEFERRED, IMMEDIATE or EXCLUSIVE. |