Sqlite, server leggero e flessibile perfettamente aderente agli standard SQL e la nuova versione 3 6.1,


Nuova versione 3.6.1 per Sqlite , server leggero e flessibile perfettamente aderente agli standard SQL

SQLite è una libreria software scritta in linguaggio C che implementa un DBMS SQL incorporabile all'interno di applicazioni. Il suo creatore è D. Richard Hipp, che lo ha rilasciato come software Open Source di pubblico dominio, privo di qualsiasi licenza. Permette di ottenere una base di dati (comprese tabelle, query, form, report) incorporate in un unico file, come il modulo Access di Microsoft Office o il modulo Base di OpenOffice.org, o prodotti specifici come Paradox o FileMaker Pro.

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SQLite è un database server leggero e flessibile perfettamente aderente agli standard SQL. Non è potente come MySQL o PostgreSQL, ma rappresenta la soluzione ideale per applicazioni embedded o comunque di dimensioni ridotte che fanno della leggerezza e della velocità di esecuzione i loro punti di forza.

Essendo una libreria, non è un processo standalone utilizzabile di per sé, ma può essere linkato all'interno di un altro programma. È utilizzabile con linguaggio C/C++ ed esistono binding anche per altri linguaggi, in particolare Tcl. È integrato nella versione 5 di PHP, consentendogli di non aver più bisogno di appoggiarsi ad un RDBMS esterno come MySQL e divenendo più concorrenziale rispetto alla piattaforma web ASP.NET di Microsoft. A sua volta MySQL è stato costretto a sviluppare la versione 5 con la gestione delle nuove tabelle InnoDB per diventare più simile/più concorrenziale ad altri importanti database "open" come PosgreSQL e Firebird.

Il pacchetto ha molte interessanti caratteristiche:

* è molto piccolo (meno di 250KB per l'intera libreria)
* è molto veloce; in molti casi più veloce di MySQL e PostgreSQL
* il codice sorgente è liberamente disponibile, chiaro e ben commentato
* è in grado di interpretare stringhe SQL, a differenza di altre librerie simili; supporta buona parte dello standard SQL92
* l'API è semplice da utilizzare
* ha transazioni atomiche, consistenti, isolate e durabili (ACID), anche in caso di crash di sistema o blackout
* è multipiattaforma
* contiene un programma di utilità che permette l'accesso al database anche manualmente (come MySQL e Postgresql e tanti altri DB) o tramite scripting
* supporta database che possono essere anche molto grandi; attualmente il limite è 2TB (241 byte)
* il database consiste di un unico file il cui formato interno è indipendente dalla piattaforma
* non ha dipendenze esterne
* normalmente non richiede alcun lavoro di amministrazione, ma supporta il comando SQL VACUUM nel caso si renda necessario

Ci sono, naturalmente, anche degli svantaggi:

* non possiede stored procedure, gestione dei permessi e molte altre funzionalità tipiche dei "colossi"
* non ha una vera gestione della concorrenza (le applicazioni che lo utilizzano, se necessario, devono implementarla)
* non offre alcuna cache per le query (e non ne ha la possibilità, non esistendo un processo server centrale)
* non ha protocolli di rete, non essendo utilizzabile come programma standalone; è possibile utilizzare un database in remoto, ma solo servendosi del filesystem del sistema operativo, con prestazioni difficilmente accettabili
* non è in grado di gestire dati binari in modo sicuro
* non supporta alcuni importanti comandi SQL:
o RIGHT e FULL OUTER JOIN
o sottoquery variabili
o transazioni annidate
o ALTER TABLE offre pochissime possibilità


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Una sua peculiarità è il gestire i "tipi" in modo molto flessibile: ogni campo può contenere qualsiasi tipo di dato (o quasi; gestito differentemente nella versione 2 e 3).

Ricordiamo che SQLite non è un server e che un database SQLite è costituito da un file binario accessibile direttamente, quindi risulta influenzato dalle restrizioni imposte dai Chmod con Php e da configurazioni legate a Php come il Safe Mode e configurazioni sicure.

L'accesso diretto ad un database SQLite non richiede username e password, mentre l'accesso remoto (http:// o ftp://), a differenza di quanto avviene nel caso dei file DBM, non è supportato dall'API Php: in entrambi i casi non si tratta di vere e proprie limitazioni, infatti stiamo parlando di un database engine pensato per essere utilizzato sulla stessa macchina in cui opera Php.

sqlite_open() consente di creare un database o di aprirlo se già esiste,

resource sqlite_open ( string filename [, int mode [, string &error_message]])

Il primo argomento, il file, è l'unico obbligatorio: per evitare effetti imprevedibili è preferibile utilizzare un percorso fisico assoluto (facilmente ricostruibile con funzioni come getcwd() e realpath()).

Al posto di un file presente sull'hard disk possiamo anche utilizzare ":memory:" per creare un database temporaneo (con vita pari alla durata dello script) residente soltanto memoria, una caratteristica che può tornare utile per caricare/scaricare provvisoriamente dati durante alcune operazioni di manipolazione.

"mode" per ora non ha nessun ruolo se non quello di segnaposto, ma in futuro avrà il compito di definire la modalità di accesso al file.


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Il terzo argomento rappresenta un contenitore per gli errori in caso di fallimento al momento dell'apertura, tuttavia non sembra funzionare come dovrebbe (specialmente in Windows), quindi al momento è consigliabile utilizzare sqlite_open() come segue.

\n";
$sqliteError.= ''.$php_errormsg.'' ;

$php_errormsg='' ;

die($sqliteError) ;

}

//altre operazioni


/*
Chiude il database
*/
sqlite_close($dbLink) ;

?>
SQLite Functions
Predefined Classes
SQLiteDatabase

Represents an opened SQLite database.

Constructor

  • __construct - construct a new SQLiteDatabase object

  • Methods

  • query - Execute a query

  • queryExec - Execute a result-less query

  • arrayQuery - Execute a query and return the result as an array

  • singleQuery - Execute a query and return either an array for one single column or the value of the first row

  • unbufferedQuery - Execute an unbuffered query

  • lastInsertRowid - Returns the rowid of the most recently inserted row

  • changes - Returns the number of rows changed by the most recent statement

  • createAggregate - Register an aggregating UDF for use in SQL statements

  • createFunction - Register a UDF for use in SQL statements

  • busyTimeout - Sets or disables busy timeout duration

  • lastError - Returns the last error code of the most recently encountered error

  • fetchColumnTypes - Return an array of column types from a particular table

  • SQLiteResult


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Represents a buffered SQLite result set.
Methods
  • fetch - Fetches the next row from the result set as an array

  • fetchObject - Fetches the next row from the result set as an object

  • fetchSingle - Fetches the first column from the result set as a string

  • fetchAll - Fetches all rows from the result set as an array of arrays

  • column - Fetches a column from the current row of the result set

  • numFields - Returns the number of fields in the result set

  • fieldName - Returns the name of a particular field in the result set

  • current - Fetches the current row from the result set as an array

  • key - Return the current row index

  • next - Seek to the next row number

  • valid - Returns whether more rows are available

  • rewind - Seek to the first row number of the result set

  • prev - Seek to the previous row number of the result set

  • hasPrev - Returns whether or not a previous row is available

  • numRows - Returns the number of rows in the result set

  • seek - Seek to a particular row number

  • SQLiteUnbuffered

Represents an unbuffered SQLite result set. Unbuffered results sets are sequential, forward-seeking only.



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Methods

  • fetch - Fetches the next row from the result set as an array

  • fetchObject - Fetches the next row from the result set as an object

  • fetchSingle - Fetches the first column from the result set as a string

  • fetchAll - Fetches all rows from the result set as an array of arrays

  • column - Fetches a column from the current row of the result set

  • numFields - Returns the number of fields in the result set

  • fieldName - Returns the name of a particular field in the result set

  • current - Fetches the current row from the result set as an array

  • next - Seek to the next row number

  • valid - Returns whether more rows are available



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  • Table of Contents



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sqlite_array_query" height="7" width="11"> SQLite
Last updated: Fri, 22 Aug 2008
add a note add a note User Contributed Notes
SQLite Functions
vincent at tigroux dot net
10-Oct-2006 03:19
on win 32

the error "malformed database schema - unable to open a temporary database file for storing temporary tables" may happen if the temp and tmp env vars are typed like this : %WINDIR/Temp

Replace by C:/Windows/Temp and the error will disappear.
papafox888 at hotmail dot com
01-Jun-2006 09:05
If you get an error message:

Warning: sqlite_open() [function.sqlite-open]: file is encrypted or is not a database

then most probably your code is accessing a SQLite3 database.

sqlite_open() only supports SQLite2. Use PDO to access SQLite3.
NOTshrockc_inhs_org
10-May-2006 10:05
The correct url for the windows dll is:

http://pecl4win.php.net/ext.php/php_sqlite.dll
Egon at example dot com
21-Feb-2006 05:15
<$php public function set_by_db_with_join_to_users_department($col, $foo){ $list = "da.ROWID, da.dept_id, da.script, da.action, da.description, ud.name"; $query = "SELECT $list FROM dept_access AS da, users_department AS ud WHERE da.dept_id = ud.ROWID AND da.$col = '$foo';"; $db = new SQLiteDatabase (dept_access::db_path, 0666, &$error) or die("Failed: $error"); $db->queryExec("ATTACH DATABASE '".dept_access::db_users_path."' AS users");
$row = $db->arrayQuery($query, SQLITE_ASSOC);
unset($db);

echo $query."\n";
echo var_dump($row);
$this->ROWID = $row[0]['da.ROWID'];
$this->dept_id = $row[0]['da.dept_id'];
$this->dept_name = $row[0]['ud.name'];
$this->script = $row[0]['da.script'];
$this->action = $row[0]['da.action'];
$this->description = $row[0]['da.description'];
}
?>

For ATTACH DATABASE to work you need to run it in a $db->queryExec(ATTACH DATABASE...); before using $db->arrayQuery. This is most likly the case with other OO methods to. This on stumped me for a while.
heinemann.juergen AT t-online.de
11-Nov-2005 09:53
Simple Example for using SQLite for small Buffering Clipboard ;)

// $Id: SQLiteClipboard.php5,v 1.1 2005/09/09 10:15:26 heinemann Exp $


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/**
* @callgraph
* @class SQLiteClipboard
* @short Simple Read/Write Clipboard Class
* @version 0.0.1
* @since Fr Sep 9 08:14:45 CEST 2005
* @code
$sqlite = new SQLiteClipboard( MY_TEMP_DIR );
if ( $sqlite->INSERTING = time() )
var_dump( $sqlite->INSERTING );
else
echo "Nothing done!";
* @endcode
*/

final class SQLiteClipboard
{
private
$SQL;
private
$DB = "Clipboard.sqlite";
private
$TB = "Clipboard";
private
$ID = "ID";
private
$PA = "PARAM";
private
$VA = "VAL";

function
__construct( $path )
{
$this->DB = chop( $path . "/" . $this->DB );
$this->sql_init();
}

private function
sql_init()
{
$this->SQL = new SQLiteDatabase( $this->DB, 0660 );
if ( !
file_exists( $this->DB ) )
die(
"Permission Denied!" );

$q = $this->SQL->query("PRAGMA table_info(" . $this->TB . ")");
if (
$q->numRows() == 0 ) {
$this->SQL->query( "CREATE TABLE " . $this->TB . " ( " . $this->ID . " INTEGER PRIMARY KEY, " . $this->PA . " CHAR(255), " . $this->VA . " CHAR(255) );" );
}
}

private function
sql_check( $p )
{
$o = null;
$q = $this->SQL->query( "SELECT " . $this->ID . " FROM " . $this->TB . " WHERE ( " . $this->PA . "='$p' ) ORDER BY " . $this->ID . " LIMIT 1" );
while(
$q->valid() ) {
$r = $q->current();
return
$r[$this->ID];
$q->next();
}
return
false;
}

public function
__get( $p )
{
$q = $this->SQL->query( "SELECT " . $this->VA . " FROM " . $this->TB . " WHERE ( " . $this->PA . "='$p' ) ORDER BY " . $this->ID );
while(
$q->valid() ) {
$r = $q->current();
$o = $r[$this->VA];
$q->next();
}
return
$o;
}

public function
__set( $p, $v )
{
if (
$this->sql_check( $p ) && ! empty( $v ) )
return
$this->SQL->query( "UPDATE " . $this->TB . " SET " . $this->VA . "='$v' WHERE ( " . $this->PA . "='$p' );" );
elseif ( !
$this->sql_check( $p ) && ! empty( $v ) )
return
$this->SQL->query( "INSERT INTO " . $this->TB . " ( " . $this->PA . ", " . $this->VA . " ) VALUES ('$p', '$v' );" );
elseif (
$this->sql_check( $p ) && empty( $v ) )
return
$this->SQL->query( "DELETE FROM " . $this->TB . " WHERE ( " . $this->PA . "='$p' );" );
else
return
false;
}

}
// end Class


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?>
31-Aug-2005 04:21
A function to check whether a table exists:

function sqlite_table_exists(&$sqlite, $table)
{
$result = $sqlite->query("SELECT name FROM sqlite_master WHERE type='table' AND name='$table'");
return
$result->numRows() > 0;
}
?>
bens at effortlessis dot com
14-Jul-2005 11:37
Sqlite by default allows for foreign keys, but doesn't enforce them.

I found a nice article on how to enforce foreign keys at http://www.justatheory.com/computers/databases/sqlite/

It would be nice if this could be handled with a wrapper class, so that adding foreign keys is done thru a wrapper API to automate the generation of the necessary enforcement triggers. If nobody's done this by the time I start coding against SqlLite/PHP5 in 6-12 months, I'll write one myself, possibly by modifying "jon at jenseng dot com"s alter table wrapper

Anyway, it's not PHP specific, but anybody using Sqlite really should know this!
Stephen Leaf
30-Jun-2005 05:58
I think it would be good to point out that currently (as of 5.0.4) this extention does not support SQLite 3 databases.
So if your getting an error message like:
Error: file is encrypted or is not a database
That is why.
bart at mediawave dot nl
18-Apr-2005 07:30
SELECT tablename.columnname FROM table;

will cause SQLite to return an array having tablename.field_name as the array index. (e.g. $result['tablename.field_name'])

To let SQLite return an array having only field_name as the array index (e.g. $result['field_name']) you can issue a 'PRAGMA short_column_names = 1' query:

sqlite_query($connection_id, 'PRAGMA short_column_names = 1');

This behaviour is more consistent with the other database extensions.

For a full list of all pragmas visit: http://sqlite.org/pragma.html
dotwho at NOSPAM dot mac dot com
09-Feb-2005 06:03
This may have been obvious to others, but I had a tough time finding the info.

The default location for the actual database file is the same location of the php doc that created the database. You can alter this behavior by specifying the full path in the creation call:



Note that if you used the default location, the db file may be served up by the webserver if it is in a the http document path. This is obviously a security risk that should be avoided.

//Max
hunreal+php at gmail dot com
16-Jan-2005 08:42
Check the db/table if exist

$db_name='db';
$db=new SQLiteDatabase($db_name, 0666, $error);
if ($error) exit($error);
$q=$db->query("PRAGMA table_info(test)");
if ($q->numRows()!=2) {
if (!@$db->queryexec("
CREATE TABLE test (
id INTEGER NOT NULL PRIMARY KEY,
text VARCHAR ( 255 ) NOT NULL
)")
) exit ("Create SQLite Database Error\n");
}


Scarica subito!


nicolas dot toniazzi at free dot fr

16-Nov-2004 07:24
The same in 3 lines.

function sqlite_table_exists($db,$mytable) {
/* counts the tables that match the name given */
$result = sqlite_query($db,"SELECT COUNT(*) FROM sqlite_master WHERE type='table' AND name='$mytable'");

/* casts into integer */
$count = intval(sqlite_fetch_single($result));

/* returns true or false */
return $count > 0;
}
?>
alexs at alphacomolex dot info
28-Oct-2004 03:41
the OO version.
function sqlite_table_exists($db,$mytable) {
// ask the database kindly what tables is has.
$result = $db->query("SELECT name FROM sqlite_master WHERE type='table'");
$tables = $result->fetchAll();
// if there's no items in the array then our taget is not going to exists.
if (count($tables) == 0) {
return
FALSE ;
}
// loop over the tables to see if there's a table we're looking for.
foreach ($tables as $table) {
if (
$table['name'] == $mytable) {
return(
TRUE);
}
}
// there was no such table, informe the user the bad news.
return(FALSE);
}
?>
artooro at gmail dot com
21-Oct-2004 06:26
If you need to check if a table exists, you can use a function like this:
//Returns TRUE if table exists and FALSE otherwise
// $mytable = table you want to check for

function sqlite_table_exists($mytable) {
$db = sqlite_open('mydb.sqlite', 0666, $sqliteerror);
$query = sqlite_query($db, "SELECT name FROM sqlite_master WHERE type='table'");
$tables = sqlite_fetch_array($query);
if (
$tables != '') {
foreach (
$tables as $table) {
if (
$table == $mytable) {
return(
"TRUE");
}
else {
return(
"FALSE");
}
}
}
else {
return(
"FALSE");
}
}
?>

A function like this could be used to create the table if it's not already created, etc.


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j-pieper at NOSPAM dot web dot de
19-Oct-2004 03:18
If you want to create a table in your database which should have an integer primary key, you cannot declare the row like this:

id int(16) primary key
or
id integer(16) primary key

When you declare it like this it could be that the id isn't auto increment. You have to declare it like this:

id integer primary key
filip at filipdewaard dot com
09-Sep-2004 11:39
I've written a short article about the (lack of) use of SQLite in-memory databases: http://www.filipdewaard.com/21_SQLite_inmemory_databases.html . Hopefully it will help somebody out there ;)
jon at jenseng dot com
20-Jul-2004 02:50
Since SQLite doesn't support ALTER TABLE statements or renaming tables, modifying an existing table is a bit cumbersome. You have to:

1. create a temporary table
2. copy the original table into the temporary table
3. delete the original
4. recreate the original with new column definitions
5. copy the contents back
6. delete the temporary table

As this is rather unwieldy, I've created a wrapper class that allows for ALTER TABLE queries and does the dirty work for you. It has integrated error handling to ensure that queries are completely valid and it allows for complex statements such as:

ALTER TABLE foo ADD bar VARCHAR(27), DROP bar2, CHANGE bar3 foobar INTEGER, ADD bar4 DATE

Documentation:
http://code.jenseng.com/db/

Source:
http://code.jenseng.com/db/sql.txt
david at acz dot org
14-Jul-2004 06:29
You can use the PECL SQLite extension as a static (built into the executable) PHP module with PHP 4. Download the extension tarball and extract it. Move it to ext/sqlite in the PHP source directory. Delete configure and run buildconf.

Example below. Change version numbers as appropriate:

$ tar -xzvf php-4.3.8.tar.gz
$ tar -xzvf SQLite-1.0.2.tgz
$ mv SQLite-1.0.2 php-4.3.8/ext/sqlite
$ cd php-4.3.8
$ rm configure
$ ./buildconf --force

If everything worked, then you should now be able to build PHP with SQLite support:

$ ./configure --help | grep sqlite
--with-sqlite Include sqlite support

I think this method will work for other PECL extensions.
13-May-2004 07:46
PHP5 compile time option --enable-sqlite-utf8

See the note about buggy utf-8 support http://uk.php.net/manual/en/function.sqlite-libencoding.php


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csaba at alum dot mit dot edu

14-Apr-2004 08:16
If you want to get the list of all the columns in a table (and associated information), PRAGMA is helpful (see http://sqlite.org/lang.html#pragma for details):

if (!($db=@sqlite_open("delme.db",0666,$sqliteerror))) die("Can't open database");
@sqlite_query ($db, 'DROP TABLE foo;');
sqlite_query($db, "CREATE TABLE foo (bar INTEGER PRIMARY KEY, baz VARCHAR(5));");
$aTableStruct = sqlite_array_query($db, "PRAGMA table_info('foo');", SQLITE_ASSOC);
for ($i=0,$aNames=array();$i ['bar', 'baz']

Note also that if you want to use more than one database in the same connection using "ATTACH DATABASE ..." then you should supply the complete database filename.

Csaba Gabor
cricket at djcricket dot com
31-Mar-2004 09:30
To elaborate on vpupkin at comcast dot net's post about the INSERT query problem, you will be unable to execute any manipulation queries (INSERT/UPDATE/DELETE/ect) on the SQLite database file unless the directory the SQLite database file resides in is writable by the webserver.

The reason for this is because SQLite needs to write a lock file to the hard drive. After a processes finishes writting, it deletes the lock file. Other processes check for the lock file before writting to the SQLite database file and if present, delay writting until the lock file is no longer present.
jlsalinas at spamsucks dot gmx dot net
13-Feb-2004 06:22
For those looking for a function similar to mysql_list_tables, here you have:

if (! function_exists ('sqlite_list_tables')) {
function sqlite_list_tables (&$dblink) {
$tables = array ();

$sql = "SELECT name FROM sqlite_master WHERE (type = 'table')";
if ($res = sqlite_query ($dblink, $sql)) {
while (sqlite_has_more($res)) {
$tables[] = sqlite_fetch_single($res);
}
}

return $tables;
}
}

And a related funtion, to test if a given table exists:

if (! function_exists ('sqlite_table_exists')) {
function sqlite_table_exists (&$dblink, $table) {
$sql = "SELECT count(name) FROM sqlite_master WHERE ((type = 'table') and (name = '$table'))";
if ($res = sqlite_query ($dblink, $sql)) {
return sqlite_fetch_single($res) > 0;
} else {
return false; // or throw exception
}
}
}

Of course it would be preferable to have these functions included in the library, to avoid potential changes internal to SQLite; but we'll have to stick to this method until then.
04-Feb-2004 08:11
Since this extension is rather new and few tutorials/articles talk about it... here's one worthy of a link:
http://www.php-mag.net/itr/online_artikel/psecom,id,447,nodeid,114


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vpupkin at comcast dot net

30-Nov-2003 08:53
if you are going to send INSERT queries, you will need to make the folder, where you put your "file.db", writable by a web server user, otherwise you'll receive error message - "Unable to open database . . . ". File permissions are not enough (phpinfo - SQLite Lib 2.8.3)

Minots Estich
21-Nov-2003 06:47
If you gone in trouble while/with installation of sqlite,
you can try the installation steps I've done at
RedHat9 with PHP4.3.4 and Apache 1.3.28
via the Linux shell:

# wget http://pecl.php.net/get/SQLite-1.0.tgz
# tar xzf SQLite-1.0.tgz
# cd sqlite
# export PHP_PREFIX="/usr"
# $PHP_PREFIX/bin/phpize
# ./configure
# make
# make install

After that add following to php.ini and restart Apache:

[sqlite]
extension="sqlite.so"

ng4rrjanbiah at rediffmail dot com
07-Nov-2003 07:19
Very nice MS PowerPoint presentation titled "SQLite and PHP" (author: Wez Furlong) can be downloaded at http://www.php.net/~wez/SQLite_and_PHP.ppt [134 KB]

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