1. Using Relational Databases and SQL
CS 122:
Using Relational Databases and SQL
Tarik Booker
Department of Computer Science
California State University, Los Angeles

2. Using Relational Databases and SQL
Part I
Databases

3. Database Definition Data (information) base (foundation)
Database - a structured collection of persistent data.
Structured: organized according to a set of rules. In this case, organized according to a database model.
Persistent: stored in permanent storage, not just RAM. If you shut down the application or the power goes off, the data is not lost.

4. Database Definition Many definitions are like this one:
A collection of data, typically modelling the activities of one or more related organizations (Ramkrishnan and Gherke, Database Management Systems.)
Keep in mind, databases don’t always model anything in particular. Database designers don’t always know what the data will be used for.

5. What is a Database? Structured using a database model
No database model, no database!
Often, not always, used to model organizational activities
Examples:
Companies
Stores
Universities

6. Database Skills Database skills are foundational in CS
The great majority of modern applications use databases to store information
You will put these skills together with your OOP programming skills a little later if you are an undergraduate, very soon if you are a grad student
As a working software engineer, you will probably use the skills you learn in this class every day

7. Database Skills
Some applications you are familiar with that rely heavily on large databases:
Wikipedia
GET
Amazon.com
ITunes
Others?

8. Physical/Logical Separation
Before DBMS, users had to implement this functionality themselves!
Traverse pointers at the physical level to extract data from a database
Far easier to abstract at the physical level!
Write a program at the logical level instead

9. Database Models The Two Levels of a Database Model The Basic Models
Physical Level (how data is stored)‏
The things we don’t have to worry about
Logical Level (how data is organized)‏
The things we do care about
The Basic Models
Hierarchical Model‏ (IBM’s IMS) represented data as a tree
Network Model (CODASYL)‏
Relational Model (ALPHA, SEQUEL)‏

10. Hierarchical Database Model

11. Hierarchical Database Model
Example of a query to retrieve info:
for book in (get_children("Programming/J.Smith”))
print book.field("Title"), book.field("Publisher")
Mostly superseded by relational model
Has an afterlife with XML

12. XML Data <CATALOG> <CD>
<TITLE>When a Man Loves A Woman</TITLE>
<ARTIST>Percy Sledge</ARTIST>
<COUNTRY>USA</COUNTRY>
<COMPANY>Atlantic</COMPANY>
<PRICE>8.70</PRICE>
<YEAR>1987</YEAR>
</CD>
<TITLE>Black Angel</TITLE>
<ARTIST>Savage Rose</ARTIST>
<COUNTRY>EU</COUNTRY>
<COMPANY>Mega</COMPANY>
<PRICE>10.90</PRICE>
<YEAR>1995</YEAR>
</CATALOG>

13. Network Model
Built on hierarchical model but allows multiple parents and multiple children

14. Relational Model Proposed by Edgar F. Codd (circa 1969)‏
Database is a collection of tables (relations)
Relational comes from ‘Relational Algebra/Calculus’ and not from ‘Relationships’
Relational model is based on extensive mathematical theory, which we will not cover in this class
Dominant database model
Oracle was the first to aggressively market a commercial relational database product

15. Dr. Edgar F(rank) Codd MA Mathematics, MA Chemistry
MS and PhD in Communication Sciences
ACM Turing Award (1981)

16. Tables‏ Artists = Table (Relation)‏
ArtistID, City, Region, ... = Columns (Attributes)‏
Each row is called a Record (Tuple)‏

17. Database Management Systems
Using Relational Databases and SQL
Part II
Database Management Systems

18. Database Management Systems (DBMS)‏
A DBMS handles these functions:
Data definition: Defining new data structures for a database, removing data structures from the database, modifying the structure of existing data.
Update: Inserting, modifying, and deleting data.
Retrieval: Obtaining information either for end-user queries and reports or for processing by applications.
Administration: Registering and monitoring users, enforcing data security, monitoring performance, maintaining data integrity, dealing with concurrency control, and recovering information if the system fails.
Source: Wikipedia

19. Database Management Systems (DBMS)‏
Some common relational DBMSs:
MySQL, PostgreSQL (free, open source)‏
Oracle, MS SQL Server (commercial)‏

20. Database Schemas The definition of the database, where you define
Tables
Relationships
Constraints
Stored Functions and Procedures
Views
Indexes
Schemas are typically represented by a schema diagram; see the Lyric diagram linked from the course page

21. Database Management Systems (DBMS)
You can have multiple databases, each with a single schema
A separate database for each application
Toystore (First database)
Bookstore (Second database)
Furniture Store (Third database)
Etc.
You can also have a single database, with multiple schemas

22. Using Relational Databases and SQL
Part III
Query Languages

23. Query Languages Query: question
Query Language = A computer language used to extract data from a database
Data Sublanguage = A computer language used to extract and manipulate database data
SEQUEL/SQL (1974)‏ developed at IBM

24. Query Languages
Data Sublanguage Alpha (Codd’s original query language)
Data Sublanguage SEQUEL (SQL)‏

25. SQL “Structured Query Language”
A non-procedural, domain-specific language (not like Java, C or C++)‏
An open ANSI and ISO standard
Supported by most major DBMS
Some variations in implementations
Used by programmers, managers, and database administrators

26. SQL SQL is “nonprocedural” or “declarative”
Procedural languages, like Java or C, require programmers to implement an algorithm (“a series of instructions that will solve a problem in a finite amount of time”) to accomplish each task
Nonprocedural / declarative languages, like SQL, require the programmer to describe *what data* s/he wants. The platform (in this case, DBMS) determines how to produce the data
This is an important distinction, but as we will see, it is not as clear-cut for SQL as it is for, say, HTML.

27. SQL Functions View information from relational databases
Single and multiple table selections
Calculation and analysis
Manipulate information in relational databases
Insert and delete records
Update records
Create relational databases
Create databases, tables, constraints, ...

28. Nonstandard Features
SQL is an open standard, but developers of DBMSs often add additional features that are not part of the standard
Differentiate their products from competitors
Vendor lock-in
What happens when you want to switch to a different DBMS?
Is it a good idea to use features like this?

29. Lyric Database Discussion
Using Relational Databases and SQL
Part IV
Lyric Database Discussion

30. Primary Keys
Primary key is used to uniquely identify every record in a table
Must be a field or combination of fields with unique values
What would happen if we needed to identify individuals in the university DB and tried to do this using first name? Last name? Both? Height? DOB?
If more than one field is required, we have a composite primary key

31. The Lyric Database
Database for a web-based company that provides services to artists and the studios that they work for
Before we start extracting data from a database, we must understand the database completely first

32. Primary Key Example What is the primary key of the Studios table?
What is the primary key of the XRefArtistsMembers table? (hint: it may require more than one field to make up a primary key!)

33. Using Relational Databases and SQL
Part V
MySQL

34. MySQL
For coursework, we will use MySQL, which you must install on a USB drive.
Bring a USB drive to the next class meeting!
You may also install it on your own laptop, but note that you will have to use the lab computers for the midterm and final exam, so be sure you can run it from a USB drive before the midterm.

35. Downloading MySQL, Part I
Go to CS122 web page and follow the links to MySQL site
Get MySQL Community Server
mysql-5.5.x has the MySQL database client and server programs
Get the .zip files (not the MSIs) for your OS (Windows vs. OSX) and processor (32 vs 64 bit).
The files are labelled in a way that may confuse you into downloading the source code, which you don’t need. Be careful to get the binaries instead. MySQL win32, for example, is 132 MB. The 27 MB file is the source code.

36. Downloading MySQL, Part II
Extract the zip files; you will have two directories
You may also want to use the MySQL Workbench, which is a GUI tool for working with MySQL. However, Workbench only works with the 32 bit version and is buggy in any case. Please don’t ask me to help you with it until at least week 3, after everyone is working smoothly with the main MySQL software.
mysql-workbench-gpl-5.2.x.... is the MySQL GUI Tools

37. Mac Users
An OSX version of MySQL is available. But you’re on your own!
If you find it hard to work with, I can give you an account on the cs1 server, which has MySQL.

38. Using MySQL In Windows Open up a Windows command line console
This process should only be slightly different in OSX
Open up a Windows command line console
Use the cd command to navigate to the
mysql-5.x.xx-xx/bin directory
If you add this directory to your PATH, you won’t have to navigate there every time. However, you *won’t* be able to add anything to the PATH on the lab computers.
Type in the following to start the database server:
start mysqld
Then type in the following to start the database client:
mysql –u root

39. Some MySQL Commands
Once MySQL has started and you see the mysql prompt:
At mysql> prompt type in: show databases;
At mysql> prompt type in: create database lyric;
At mysql> prompt type in: use lyric;
At mysql> prompt type in: show tables;
You shouldn’t see any yet

40. Adding Data to a Database
Now that the database is selected, let's load a database script
Download lyric.sql from the course webpage
At mysql> prompt type in: source [path] lyric.sql;
Where [path] stands for the path to the location where you saved lyric.sql.
If you put lyric.sql in mysql’s bin directory, all you will have to type is source lyric.sql
You should see a bunch of messages like this: Query OK, 1 rows affected (0.01 sec).

41. Verify that the database is set up
To check whether everything has worked correctly, type
SELECT * FROM Salespeople;
The output should look like this:
| SalesID | FirstName | LastName | Initials | Base | Supervisor |
| | Bob | Bentley | bbb | | |
| | Lisa | Williams | lmw | | |
| | Clint | Sanchez | cls | | |
| | Scott | Bull | sjb | NULL | NULL |
4 rows in set (0.39 sec)

42. Using MySQL in the lab
If you will be using your own laptop in the lab, bring it to the next class meeting
If you will be using MySQL on a lab computer, *bring a USB drive to the lab* on Wednesday