PHP 101 (PART 9): SQLITE MY FIRE! - PART 2
PHP 101 (PART 9): SQLITE MY FIRE! - PART 1
Not My Type
Starting From Scratch
A Few Extra Tools
Not My Type
Whilst on the topic of INSERT, remember my statement a couple pages
back about how SQLite is typeless and so you can insert values of any
type into any field? There is one important exception to this rule: a
field marked as INTEGER PRIMARY KEY. In SQLite, fields marked as
INTEGER PRIMARY KEY do two important things: they provide a unique
numeric identifier for each record in the table, and if you insert a
NULL value into them, SQLite automatically inserts a value that is 1
greater than the largest value already present in that field.
INTEGER PRIMARY KEY fields in SQLite thus perform the equivalent of
AUTO_INCREMENT fields in MySQL, and are a convenient way of
automatically numbering your records. Obviously, you can't insert
non-numeric values into such a field, which is why I said they were an
exception to the typeless rule. Read more about this at
http://www.sqlite.org/datatypes.html.
Since the books table used in the previous example already contains
such a field (the id field), it's clear that every INSERT into it with a
NULL value for that field generates a new record number. If you'd like
to retrieve this number, PHP has a way to do that too - just use the
sqlite_last_insert_rowid() function, which returns the ID of the
last inserted row (equivalent to the mysql_insert_id() function
in PHP's MySQL API).
To see this in action, update the if() loop in the middle of the
previous script to include a call to sqlite_last_insert_rowid(), as
follows:
<?php
// check to see if the form was submitted with a new record
if (isset($_POST['submit'])) {
// make sure both title and author are present
if (!empty($_POST['title']) && !empty($_POST['author'])) {
// generate INSERT query
$insQuery = "INSERT INTO books (title, author) VALUES (\"".sqlite_escape_string($_POST['title'])."\", \"".sqlite_escape_string($_POST['author'])."\")";
// execute query
$insResult = sqlite_query($handle, $insQuery) or die("Error in query: ".sqlite_error_string(sqlite_last_error($handle)));
// print success message
echo "<i>Record successfully inserted with ID ".sqlite_last_insert_rowid($handle)."!</i><p />";
}
else {
// missing data
// display error message
echo "<i>Incomplete form input. Record not inserted!</i><p />";
}
}
?>
If you need to, you can also find out how many rows were affected using
the sqlite_changes() function - try it for yourself and see!
Starting From Scratch
You'll remember, from the beginning of this tutorial, that I suggested
you initialize the library.db database using the SQLite
commandline program. Well, that isn't the only way to create a fresh
SQLite database - you can use PHP itself to do this, by issuing the
necessary CREATE TABLE and INSERT commands
through the sqlite_query() function. Here's how:
<?php
// set path of database file
$db = $_SERVER['DOCUMENT_ROOT']."/../library2.db";
// open database file
$handle = sqlite_open($db) or die("Could not open database");
// create database
sqlite_query($handle, "CREATE TABLE books (id INTEGER PRIMARY KEY, title VARCHAR(255) NOT NULL, author VARCHAR(255) NOT NULL)") or die("Error in query: ".sqlite_error_string(sqlite_last_error($handle)));
// insert records
sqlite_query($handle, "INSERT INTO books (title, author) VALUES ('The Lord Of The Rings', 'J.R.R. Tolkien')") or die("Error in query: ".sqlite_error_string(sqlite_last_error($handle)));
sqlite_query($handle, "INSERT INTO books (title, author) VALUES ('The Murders In The Rue Morgue', 'Edgar Allan Poe')") or die("Error in query: ".sqlite_error_string(sqlite_last_error($handle)));
sqlite_query($handle, "INSERT INTO books (title, author) VALUES ('Three Men In A Boat', 'Jerome K. Jerome')") or die("Error in query: ".sqlite_error_string(sqlite_last_error($handle)));
sqlite_query($handle, "INSERT INTO books (title, author) VALUES ('A Study In Scarlet', 'Arthur Conan Doyle')") or die("Error in query: ".sqlite_error_string(sqlite_last_error($handle)));
sqlite_query($handle, "INSERT INTO books (title, author) VALUES ('Alice In Wonderland', 'Lewis Carroll')") or die("Error in query: ".sqlite_error_string(sqlite_last_error($handle)));
// print success message
echo "<i>Database successfully initialized!";
// all done
// close database file
sqlite_close($handle);
?>
Or, in PHP 5, you can use the object-oriented approach:
<?php
// set path of database file
$file = $_SERVER['DOCUMENT_ROOT']."/../library3.db";
// create database object
$db = new SQLiteDatabase($file) or die("Could not open database");
// create database
$db->query("CREATE TABLE books (id INTEGER PRIMARY KEY, title VARCHAR(255) NOT NULL, author VARCHAR(255) NOT NULL)") or die("Error in query");
// insert records
$db->query("INSERT INTO books (title, author) VALUES ('The Lord Of The Rings', 'J.R.R. Tolkien')") or die("Error in query");
$db->query("INSERT INTO books (title, author) VALUES ('The Murders In The Rue Morgue', 'Edgar Allan Poe')") or die("Error in query");
$db->query("INSERT INTO books (title, author) VALUES ('Three Men In A Boat', 'Jerome K. Jerome')") or die("Error in query");
$db->query("INSERT INTO books (title, author) VALUES ('A Study In Scarlet', 'Arthur Conan Doyle')") or die("Error in query");
$db->query("INSERT INTO books (title, author) VALUES ('Alice In Wonderland', 'Lewis Carroll')") or die("Error in query");
// print success message
echo "<i>Database successfully initialized!";
// all done
// destroy database object
unset($db);
?>
A Few Extra Tools
Finally, the SQLite API also includes some ancillary functions, to
provide you with information on the SQLite version and encoding, and on
the error code and message generated by the last failed operation. The
following example demonstrates the sqlite_libversion() and
sqlite_libencoding() functions, which return the version number
and encoding of the linked SQLite library respectively:
<?php
// version
echo "SQLite version: ".sqlite_libversion()."<br />";
// encoding
echo "SQLite encoding: ".sqlite_libencoding()."<br />";
?>
When things go wrong, reach for the sqlite_last_error()
function, which returns the last error code returned by SQLite. Of
course, this error code - a numeric value - is not very useful in
itself; to convert it to a human-readable message, couple it with the
sqlite_error_string() function. Consider the following
example, which illustrates by attempting to run a query with a
deliberate error in it:
<?php
// set path of database file
$db = $_SERVER['DOCUMENT_ROOT']."/../library.db";
// open database file
$handle = sqlite_open($db) or die("Could not open database");
// generate query string
// query contains a deliberate error
$query = "DELETE books WHERE id = 1";
// execute query
$result = sqlite_query($handle, $query) or die("Error in query: ".sqlite_error_string(sqlite_last_error($handle)));
// all done
// close database file
sqlite_close($handle);
?>
Here's what the output looks like:
Note that although they might appear similar, the sqlite_last_error()
and sqlite_error_string() functions don't work in exactly the same way
as the mysql_errno() and mysql_error() functions. The
mysql_errno() and mysql_error() functions
can be used independently of each other to retrieve the last error code
and message respectively, but the sqlite_error_string() is dependent
on the error code returned by sqlite_last_error().
And that's about all I have for you in this tutorial. More secrets await you in Part 10 of PHP 101, so make sure you come back for that one!
Copyright Melonfire, 2004 (http://www.melonfire.com). All rights reserved.
Comments