C S E 3 7 3

SQLite

Outline

� Introduction to SQL

� SQLite

� SQLite Shell

� SQLite From A Program� SQLite From A Program

� An example in Java

� Conclusions

SQL

Quick Introduction To SQL

� The Structured Query Language (SQL) is a programming language designed to interact with relational databases� The SQL anagram can be pronounced either S-Q-L or sequel

� SQL is designed to work with databases that are composed of tables

The columns are data typed fields� The columns are data typed fields

� The rows are instances of data

� Relationships can be established between the columns of tables

� The formal description of the names and structure of the tables in a database is called a schema� Often the schema is the series of SQL statements that create the tables,

relationships and constraints

Quick Introduction To SQL

� There are four basic functions of any storage system (CRUD)� Create

� Read

� Update

� Delete

� The statements in SQL that support CRUD are:� The statements in SQL that support CRUD are:� CREATE TABLE - Create

� INSERT - Create

� SELECT - Read

� UPDATE – Update

� ALTER TABLE - Update

� DELETE – Delete

� DROP - Delete

SQL – CREATE TABLE

� The CREATE TABLE statement is used in SQL to create a

new table in a database

CREATE TABLE My_table(

my_field1 INT,

my_field2 VARCHAR(50),

my_field3 DATE NOT NULL,

PRIMARY KEY (my_field1, my_field2)

);

SQL – Primary And Foreign Keys

� Primary keys are a constraint on a table that specifies that the

columns (or column) that are specified as the primary key

must have a unique combination for each row in the table

� Usually we are using the primary key as the identifying information for a

row. For example {Student ID}, {SSN}, {Name, Date of Birth, Phone number}

can all be primary keys that would identify a person in a databasecan all be primary keys that would identify a person in a database

� Foreign keys are relationships between the columns of two

tables that act as constraint stating that the combination of

the values of the columns in the foreign key must exist in the

primary key of another table

� Usually this is used to state the row in the table with the foreign key is the

same entity as the row in the table with the primary key

SQL - INSERT

� The INSERT statement is add rows to the a table in a

database

INSERT INTO My_table

(field1, field2, field3)

VALUES

('test', 'N', 8/21/2013);

SQL - SELECT

� The SELECT statement is used to send query to a database

and obtained results for the query

SELECT * FROM My_table;

SELECT (my_field1, my_field3)

FROM My_table

WHERE

my_field1 > 12

AND myField2 = ‘Bob’;

SQL - UPDATE

� The UPDATE statement is used to change the value of

field in a row in the database

UPDATE My_table

SET field1 = 0

WHERE field2 = 'N';

SQL – ALTER TABLE

� The ALTER TABLE statement is used to change the

structure of a table

ALTER TABLE My_table

ADD my_field4 NUMBER(3) NOT NULL;

ALTER TABLE My_table

DROP my_field1;

SQL - DELETE

� The DELETE statement is used to delete rows from table in the database

DELETE FROM My_table

WHERE field2 = 'N';WHERE field2 = 'N';

� The TRUNCATE TABLE statement is used to quickly delete all data in a table

TRUNCATE TABLE My_table;

SQL - DROP

� The DROP statement is used to delete a table from the

database

DROP TABLE My_table;

More SQL

� SQL is a fairly large language and has a lot features and a

lot of syntax

� Some important features that weren’t covered include

� Procedures

� Constraints� Constraints

� Permissions

� This was just meant as a quick crash course to provide the

bare bones of what is needed to go over a pretty neat

database system

SQLite

Database Systems

� There are a number of database systems that you use

including mySQL, Oracle, SQLServer, and PostgreSQL

� Most of these databases are designed to be running all

the time and run as a separate process

What if we don’t want or need the database to be � What if we don’t want or need the database to be

running all the time? Or what if we are only storing data

for a single user in a single application ?

SQLite

� SQLite is a very lightweight C library that allows SQL

queries to sent to a local flat file

� Can be pronounced either S-Q-L-lite or Sequel-lite

� Additionally, since SQLite is a library it doesn’t run as a

separate process but rather is invoked from another separate process but rather is invoked from another

program

� SQLite is accessible from most programming

languages(maybe all)

� The source code for SQLite is in the public domain and so

it is viewable and modifiable

Uses Of SQLite

� Arguably SQLite is the most commonly used database in

the world

� Most SQLite users aren’t aware they are using it

� Firefox, Chrome, Safari and other web browsers

Store bookmarks, settings, browsing history� Store bookmarks, settings, browsing history

� Android and iOS

� Email Readers

� Emails, Contact Lists

� Microsoft has a similar system that it uses for the same

purposes

SQL In SQLite

� At this point SQLite supports almost all of SQL

� There are some missing features in joins, altering tables,

triggers, and supporting permissions

� In my experience there is also some places where SQLite

can be somewhat strangecan be somewhat strange

� SQLite wont enforce foreign keys unless you tell it to every time you

access the database

� The documentation for SQLite is pretty comprehensive

� http://www.sqlite.org/docs.html

SQLite Datatypes

� SQLite only has five datatypes

� NULL – For null values

� INTEGER – A 1 to 8 byte signed integer

� REAL – An 8byte floating point values

� TEXT – A text string

� BLOB – Data that stored in such a way that it is unchanged for how it was input

� Any other datatype you want to support needs to modified to fit into one of these datatypes

� Boolean – Usually an integer is used

� Date/Time – Built-in date/time functions can be used to store them in TEXT, REAL or INTEGER formats

The SQLite Shell

SQLite Shell

� SQLite provides an executable command line shell that

can be used to create and interact with a SQLite database

directly

� The pre-compiled shell can be obtained off the

downloads on the SQLite homepage for Windows, Linux downloads on the SQLite homepage for Windows, Linux

and OS X

� http://www.sqlite.org/download.html

� The shell is portable and so doesn’t require any

installation or installed libraries

SQLite Shell

� There are several commands available from within the

shell including:

� .databases – lists all the currently loaded databases

� .schema – lists the schema for the database(s)

� .tables – lists the names of all tables

� .read – will execute the SQL in the specified file

� .echo – repeats the commands inputted

� .quit – quits the shell

� .help – lists all commands

SQLite Data Browser

� Creating a new SQLite database is as easy as creating a new file� SQLite doesn’t enforce any requirements on the file extension for a SQLite

database

� Popular file extensions include .db and .sqlite3 or no extension at all

� Opening a SQLite database with the shell involves providing � Opening a SQLite database with the shell involves providing the file name as a command line argument� sqlite3 mydb.sqlite

� If you are already in the shell you can use:

� attach “mydb.sqlite” as db1;

� Once you are in the shell you can then start entering and executing SQL queries and statements

SQLite From A Program

SQLite From A Program

� SQLite provides a C/C++ as well as a Tcl API

� There are numerous bindings that allow SQLite to be used

from just about any programming language

� Java

Python� Python

� .Net

� Javascript

� The SQLite wiki maintains a list of bindings by language

� http://www.sqlite.org/cvstrac/wiki?p=SqliteWrappers

SQLite From A Program

� I’m going to go over a simple example of how to use Java

to interact with a SQLite database

� I used a simple JDBC driver to interface with SQLite

� https://bitbucket.org/xerial/sqlite-jdbc

There are other ways to use SQLite from Java� There are other ways to use SQLite from Java

Installing The Driver In Eclipse

� First we download the .jar file for the driver

� “sqlite-jdbc-3.7.2-javadoc.jar”

� Place the .jar into a directory named “lib” in the project’s

directory

Refresh the project in Eclipse� Refresh the project in Eclipse

� Right click on the project in the package explorer

� Now we are ready to start using SQLite

Using SQLite

� Lets take a walk through the code for a simple example

Conclusions

� SQLite is a very simple and easy to use database system

� It allows for very portable databases and drops the

requirement of a database system running around the

clock

It can be accessed from just about any programming � It can be accessed from just about any programming

language or just from a command line shell

Questions?