Introduction to SQLite

ISYS 475

Download SQLite

• http://sqlite.org/download.html– Precompiled Binaries for Windows

• Create a folder “sqlite” under c:\xampp and copy the downloaded program to the folder.

Introduction• SQLite is a database system that is: – self-contained: It requires very minimal support from

external libraries;– Serverless: reads and writes directly from the database files

on disk and requires no intermediary server process. SQLite itself is the server.

– zero-configuration: It does not need to be "installed" before it is used. There is no "setup" procedure;

– transactional: all changes and queries appear to be Atomic, Consistent, Isolated, and Durable (ACID) that can survives system failure.

– It is small. A typical installation occupies only about 256K on your drive.

Where are good places to use it?

• In desktop applications. SQLite makes a great application file format. You can use SQL, don't have to design your own file format.

• For smaller websites. SQLite should be able to manage a site that gets under 100,000 hits a day easily. In other words, most websites would be fine with SQLite as the database.

• •For embedded devices. The uses in the iPhone and Symbian are good examples of this.

Two Ways of Working with SQLite

• SQLite Command Line• PHP/SQLite

Starting SQLite Command Line• To start the sqlite3 program from the Windows command prompt, just

type "sqlite3" followed by the name the file that holds the SQLite database. If the file does not exist, a new one is created automatically.

• Note: The standard extension for SQLite database is “.sqlite”

Helpful links

• Command line commands: – http://www.sqlite.org/sqlite.html– http://www.pantz.org/software/sqlite/

sqlite_commands_and_general_usage.html

For a listing of the available dot commands, you can enter ".help" at any time

.read FILENAME

• Execute SQL in FILENAME

sqlite> .read c:\\teaching\\475\\MySQLOrder.txt

sqlite> .tablescustomers odetails orders products salesreps tbl1

Note: Need the escape character, “\\”

.databases• List names and files of attached databases

sqlite> .databaseseq name file

--- --------------- ------------------------------------

0 main c:\xampp\Sqlite\salesdb.sqlite

sqlite>

.tables

• List names of tables

sqlite> .tablescustomers odetails orders products salesreps

.schema

• Show the CREATE statements

sqlite> .schemaCREATE TABLE customers (cid char(3), cname varchar(20), rating char(1),city varchar(20));CREATE TABLE odetails(oid char(3), pid char(3),qty decimal(5,1));CREATE TABLE orders(oid char(3), cid char(3),sid char(3),odate date);CREATE TABLE products(pid char(7), pname varchar(15), price decimal(6,2),onhand decimal(5,1));CREATE TABLE salesreps(sid char(3),sname varchar(20),phone char(4));CREATE TABLE tbl1(one varchar(10), two smallint);

.backup

• sqlite> .backup c:\\xampp\\sqlite\\backup.txt

.mode MODE • Set output mode where MODE is one of:• csv Comma-separated values• column Left-aligned columns. • html HTML <table> code• insert SQL insert statements for TABLE• line One value per line• list Values delimited by .separator string

• tabs Tab-separated values• tcl TCL list elements

sqlite> .mode listsqlite> select * from tbl1;

Set output to html

sqlite> .mode htmlsqlite> select * from customers;<TR><TD>C1</TD><TD>MYERS</TD><TD>A</TD><TD>CHICAGO</TD></TR><TR><TD>C2</TD><TD>GOODMAN</TD><TD>A</TD><TD>SAN FRANCISCO</TD></TR><TR><TD>C3</TD><TD>LEE</TD><TD>B</TD><TD>CHICAGO</TD></TR><TR><TD>C4</TD><TD>GRAUER</TD><TD>C</TD><TD>LOS ANGELES</TD></TR>

Other Commands

• .output FILENAME Send output to FILENAME

• .output stdout Send output to the screen• .quit

PHP and SQLite

http://www.php.net/manual/en/book.sqlite.php

PHP Links to SQLite

• This is an extension for the SQLite Embeddable SQL Database Engine. SQLite is a C library that implements an embeddable SQL database engine. Programs that link with the SQLite library can have SQL database access without running a separate RDBMS process.

• SQLite is the server. The SQLite library reads and writes directly to and from the database files on disk.

Run phpinfo();http://localhost/xampp/

Two Ways of Working with SQLite

• Using PDO commands• Using PHP/SQLIte commands

Working with an existing Sqlite database with PDO

• DSN: sqlite:absolute path to database• Example:

sqlite:c:\\xampp\\Sqlite\\salesdb.sqlite

Define a database handler

2. Connecting to a database at a specified path:

$db = new PDO("sqlite:c:\\xampp\\Sqlite\\salesdb.sqlite");

1. Connecting to a database in the current project folder:

$db = new PDO("sqlite:SalesDB.sqlite");

Run SQL SELECT command and fetch records

<?php<?php $db = new PDO("sqlite:c:\\xampp\\sqlite\\salesdb.sqlite"); $result=$db->query("SELECT * FROM customers"); $result->setFetchMode(PDO::FETCH_ASSOC); while($row = $result->fetch()) { echo $row['cid'] . " " . $row['cname'] . " " . $row['city'] . " " . $row['rating'] . "<br>";

} ?>

Using foreach

<?php $db = new PDO("sqlite:c:\\xampp\\sqlite\\salesdb.sqlite"); $result=$db->query("SELECT * FROM customers"); $result->setFetchMode(PDO::FETCH_ASSOC); foreach ($result as $row) { echo $row['cid'] . " " . $row['cname'] . " " . $row['city'] . " " . $row['rating'] . "<br>"; } ?>

Use PDO exec to run Insert

<?php $db = new PDO("sqlite:c:\\xampp\\sqlite\\salesdb.sqlite"); $db->exec("INSERT INTO customers VALUES ('c6','chen','sf', 'a')"); ?>

Use PDO exec to run Delete

<?php $db = new PDO("sqlite:c:\\xampp\\sqlite\\salesdb.sqlite"); $count = $db->exec("DELETE FROM customers WHERE cid = 'c6'"); print("Deleted $count rows.\n"); ?>

Use PDO to create a new sqlite database

• DSN: sqlite:absolute path to database• Example:

sqlite:customer.sqlitesqlite:c:\\xampp\\sqlite\\customer.sqlite

Note: If the database does not exist, SQLite will create it. But we need to execute SQL CREATE TABLE command to create tables.

Define a database handler

2. Creating a new database at a specified path:

$db = new PDO("sqlite:c:\\xampp\\sqlite\\customer.sqlite");

1. Creating a new database in the current project folder:

$db = new PDO("sqlite:customer.sqlite");

Creating a New SQLite Table

• Use exec() command to run the CREATE TABLE command:

$db->exec('CREATE TABLE customer (cid CHAR(5) PRIMARY KEY, cname CHAR(25), city CHAR(25), rating CHAR(1))');

Run SQL Insert commands to add records

<?php $db = new PDO("sqlite:c:\\xampp\\sqlite\\customer.sqlite"); $db->exec('CREATE TABLE customer (cid CHAR(5) PRIMARY KEY, cname CHAR(25), city CHAR(25), rating CHAR(1))'); $db->exec("INSERT INTO customer VALUES ('c1','peter','sf', 'a')"); $db->exec("INSERT INTO customer VALUES ('c2','paul','la', 'b')"); $db->exec("INSERT INTO customer VALUES ('c3','mary','sf', 'a')"); ?>

Run SQL SELECT command and fetch records

<?php $db = new PDO("sqlite:c:\\xampp\\sqlite\\customer.sqlite");$result=$db->query("SELECT * FROM customer");$result->setFetchMode(PDO::FETCH_ASSOC); foreach ($result as $row) {echo $row['cid'] . " " . $row['cname'] . " " . $row['city'] . " " . $row['rating'] . "<br>"; } ?>

Using PHP/SQLIte3 classhttp://www.php.net/manual/en/sqlite3.close.php

• SQLite3::__construct — Instantiates an SQLite3 object and opens an SQLite 3 database

• SQLite3::query — Executes an SQL query and returns a SQLite3Result class

• •SQLite3Result::fetchArray — Fetches a result row as an associative or numerically indexed array or both

• SQLite3::exec — Executes a result-less query against a given database

• SQLite3::changes — Returns the number of database rows that were changed (or inserted or deleted)

• SQLite3::close — Closes the database connection

Working with SQLite3 class

<?php $db = new SQLite3("c:\\xampp\\sqlite\\customer.sqlite"); $result=$db->query("SELECT * FROM customer"); while($row = $result->fetchArray()) { echo $row['cid'] . " " . $row['cname'] . " " . $row['city'] . " " . $row['rating'] . "<br>"; } ?>

Adding a record

<?php $db = new SQLite3("c:\\xampp\\sqlite\\customer.sqlite"); $db->exec("INSERT INTO customer VALUES ('c6','chen','sf', 'a')"); echo $db->changes() . 'record added'; ?>

Deleting a record

<?php $db = new SQLite3("c:\\xampp\\sqlite\\customer.sqlite"); $db->exec("DELETE FROM customer WHERE cid = 'c6'"); echo $db->changes() . 'record deleted'; ?>

In-memory database

• An in-memory database (IMDB; also main memory database system or MMDB) is a database management system that primarily relies on main memory for computer data storage. It is contrasted with database management systems which employ a disk storage mechanism. Main memory databases are faster than disk-optimized databases since the internal optimization algorithms are simpler and execute fewer CPU instructions. Accessing data in memory eliminates seek time when querying the data, which provides faster and more predictable performance than disk

Creating SQLite Database in Memory

• DSN: sqlite::memory:– Example:

$db = new PDO("sqlite::memory:");Note: there is a “:” after the word memory.

• The database ceases to exist as soon as the database connection is closed.

• opening two database connections each with the filename ":memory:" will create two independent in-memory databases.

In Memory Database Example

<?php $db = new PDO("sqlite::memory:"); $db->exec('CREATE TABLE customer (cid CHAR(5) PRIMARY KEY, cname CHAR(25), city CHAR(25), rating CHAR(1))'); $db->exec("INSERT INTO customer VALUES ('c1','peter','sf', 'a')"); $db->exec("INSERT INTO customer VALUES ('c2','paul','la', 'b')"); $db->exec("INSERT INTO customer VALUES ('c3','mary','sf', 'a')"); $result=$db->query("SELECT * FROM customer"); $result->setFetchMode(PDO::FETCH_ASSOC); foreach ($result as $row) { echo $row['cid'] . " " . $row['cname'] . " " . $row['city'] . " " . $row['rating'] . "<br>"; } ?>

ATTACH DATABASE

• The ATTACH DATABASE statement adds another database file to the current database connection.

• Example: – ATTACH DATABASE "FromDisk.sqlite" AS diskdb;

• Tables in an attached database can be referred to using the syntax database-name.table-name.

Copy Disk Database to Memory

<?php $dbMemo = new PDO('sqlite::memory:'); $dbMemo->exec('ATTACH "c:\\xampp\\sqlite\\salesdb.sqlite" AS diskdb'); $dbMemo->exec('create table customer as select * from diskdb.customers'); $dbMemo->exec('DETACH diskdb'); $result=$dbMemo->query("SELECT * FROM customer"); $result->setFetchMode(PDO::FETCH_ASSOC); foreach ($result as $row) { echo $row['cid'] . " " . $row['cname'] . " " . $row['city'] . " " . $row['rating'] . "<br>"; } ?>

Copy Memory Database to disk

<?php $db = new PDO("sqlite::memory:"); $db->exec('CREATE TABLE customer (cid CHAR(5) PRIMARY KEY, cname CHAR(25), city CHAR(25), rating CHAR(1))'); $db->exec("INSERT INTO customer VALUES ('c12','peter','sf', 'a')"); $db->exec("INSERT INTO customer VALUES ('c22','paul','la', 'b')"); $db->exec("INSERT INTO customer VALUES ('c32','mary','sf', 'a')"); $result=$db->query("SELECT * FROM customer"); $result->setFetchMode(PDO::FETCH_ASSOC); foreach ($result as $row) { echo $row['cid'] . " " . $row['cname'] . " " . $row['city'] . " " . $row['rating'] . "<br>"; } $db->exec('ATTACH "c:\\xampp\\sqlite\\customer.sqlite" AS diskdb'); $db->exec('insert into diskdb.customer select * from customer'); $db->exec('DETACH diskdb'); $dbSave = new PDO('sqlite:c:\\xampp\\sqlite\\customer.sqlite'); $result=$dbSave->query("SELECT * FROM customer"); $result->setFetchMode(PDO::FETCH_ASSOC); foreach ($result as $row) { echo $row['cid'] . " " . $row['cname'] . " " . $row['city'] . " " . $row['rating'] . "<br>"; } ?>