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Using Relational Databases and SQL

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Title: Using Relational Databases and SQL


1
Using Relational Databases and SQL
Lecture 1 Introduction
John Hurley Department of Computer
Science California State University, Los Angeles
2
Introduction
  • John Hurley
  • Call me John, especially outside class.
  • If thats too informal for you, you can call me
    Instructor
  • hurley_j_at_sbcglobal.net
  • xxx6aTWOb VI Xxx4cATEd
  • d7xxx8eONEf5gFORE!hij
  • (text preferred)
  • Office hours listed on course page. I will often
    be in A-310A (inside A-310) at other times, too.

3
Attendance
4
Administrative
  • Course page
  • http//www.calstatela.edu/faculty/jhurley2/classes
    /cs122
  • Syllabus
  • Software download links
  • Assignment dates

5
Grading
  • Grading A, B, C, (with and -), NC.
  • If you are an undergraduate and dont get a C or
    better, you get an NC
  • If you are a graduate student and dont get a B
    or better, you get an NC
  • See the grading scale on the syllabus no curve
  • In past terms, I have assigned all grades from A
    to C as well as NC in this class. Median grade
    is usually B or B, which is lower than the
    median grade in my CS120 sections.

6
Deadbeats Will Fail!
  • About 10 of the all the course grades I have
    ever given in CS122 were NCs. Everyone to whom I
    have ever given an NC missed significant portions
    of the coursework.
  • If you decide not to take the class, drop it
    yourself. Dont expect me to drop you!
  • I cant drop anyone after the no-record drop
    deadline
  • You will have your midterm grades before the
    drop-with- W deadline

7
Labs
  • Assignments are in text files linked from the
    course web page
  • Turn in on CSNS
  • Posted before the weekly lecture
  • Part A usually due at the end of the weeks lab
    class
  • Part B usually due before the following weeks
    lecture
  • Let me know in advance if you wont be able to
    attend a lab for some good reason
  • I may give quizzes towards the end of lab periods
    if attendance is poor.
  • Last labs before the midterm and final will be
    ungraded, very realistic practice exams.

8
Assignments
  • Labs and exams will contain the following types
    of questions
  • short answers and multiple choice
  • 1-paragraph answers
  • SQL to English
  • English to SQL

9
Quizzes
  • Quizzes will be administered either during
    lectures or labs
  • Quizzes usually unannounced but open-notes
  • I may give one pre-announced closed-book quiz
    which requires you to memorize a few very
    important definitions
  • No makeups unless you provide a satisfactory
    explanation in advance for why you wont be in
    class.

10
Cheating
  • You may discuss general material about databases
    and the techniques taught in this class with
    other students
  • You may give or receive help understanding
    assignments and debugging work

11
Cheating
  • You may copy examples from the lecture notes and
    then change them to meet assignment requirements.
  • Working programmers often solve problems in
    similar ways.
  • Other instructors may not allow this. I am
    only saying that it is OK and expected in my
    sections of CS122.
  • You may not directly use language from the
    lecture notes to answer short-answer questions
    restate the answers in your own words. This is
    difficult to do thats the point.

12
Cheating Copying
  • There are grey areas in cheating in CS, but
    presenting an answer that is copied directly from
    any source other than your brain is always over
    the line.
  • You may not copy code from other students or
    allow anyone to copy your code.
  • Few to none of my assignment questions are taken
    from the textbook or other sources, so dont
    bother copying published solutions to the
    textbook exercises.
  • If you copy code posted by past students, you
    will likely do poorly anyway, because I change
    many questions slightly each term.

13
Cheating on LAB WORK
  • OK on lab work
  • Copying examples from the lecture notes and
    modifying them to fulfill the assignment
  • Examples of legitimate help for other students
  • The problem with your query is that you forgot
    to write the join condition
  • That isnt working because on a Mac the table
    name is case sensitive
  • You accidentally copied a character from
    Powerpoint that is invalid in mySQL
  • You need to use a float instead of an int for
    that field because the values might not be an
    integer
  • Cheating on lab work
  • Copying code from other students or internet
    sources
  • Copying text from other students for short-answer
    or essay questions
  • Copying text from the internet or a book for
    short-answer and essay questions

14
Cheating on Exams and Quizzes
  • OK on exams and open-book quizzes
  • Consulting lecture notes, textbooks, your own
    notes
  • Checking Wikipedia or other internet sources that
    do not involve real-time communication with human
    beings
  • Copying examples from the lecture notes and
    modifying them to answer the questions
  • Cheating on exams and quizzes
  • Copying code or text from other students or
    internet sources
  • Answering short-answer questions with direct
    quotes form the notes (restate them in your own
    words!)
  • Communicating with any human being other than me
    via email, chat, phone, or any other means

15
Cheating Detection
  • It is obvious to me when students answer
    short-answer questions with text copied from
    professional-level sources like Wikipedia and
    textbooks.
  • Even for SQL code, there are only a few correct
    answers to each question using the material we
    cover. However, if you copy answers from other
    students, you will sooner or later copy an
    identifiable incorrect answer or trip up in some
    other way.
  • I will be comparing all students lab and exam
    papers using an automatic tool designed to
    detect copying. I developed this application
    specifically to detect cheating in CS122!
  • If I do detect copying, I will penalize all
    students involved equally. If you understand the
    material, it is foolish to take this risk by
    letting other students copy your work.
  • People who do well on labs but poorly on exams
    and quizzes receive careful scrutiny!

16
Using Relational Databases and SQL
Part I Databases
17
Database Definition
  • Data (information) base (foundation)
  • A database is 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.

18
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.)
  • I dont like this definition, because databases
    dont always model anything in particular.
    Database designers dont always know what the
    data will be used for.

19
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

20
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

21
Database Skills
  • Some applications you are familiar with that rely
    heavily on large databases
  • Wikipedia
  • GET
  • Amazon.com
  • ITunes

22
Tables?
  • User can add and remove tables, get information
    from them, update or delete information in them,
    change them
  • These are the skills we will study in this class

23
Database Background
  • Storage was bulky, expensive, and slow in the old
    days!

24
Physical/Logical Separation
  • Previous to the inventions of DBMS, one had to
    write a program that traversed pointers at the
    physical level to extract data from a database
  • By abstracting the physical level and writing a
    program at the logical level instead, extracting
    data from a database became much easier

25
Database Models
  • The Two Levels of a Database Model
  • Physical Level (how data is stored)?
  • The things we dont have to worry about
  • Logical Level (how data is organized)?
  • The things we do care about
  • The Basic Models
  • Hierarchical Model? (IBMs IMS) represented data
    as a tree
  • Network Model (CODASYL)?
  • Relational Model (ALPHA, SEQUEL)?

26
Hierarchical Database Model
27
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

28
XML Data
ltCATALOGgt ltCDgt ltTITLEgtWhen a Man Loves A
Womanlt/TITLEgt ltARTISTgtPercy Sledgelt/ARTISTgt ltC
OUNTRYgtUSAlt/COUNTRYgt ltCOMPANYgtAtlanticlt/COMPANYgt
ltPRICEgt8.70lt/PRICEgt ltYEARgt1987lt/YEARgt lt/CDgt
ltCDgt ltTITLEgtBlack Angellt/TITLEgt ltARTISTgtSavag
e Roselt/ARTISTgt ltCOUNTRYgtEUlt/COUNTRYgt ltCOMPANY
gtMegalt/COMPANYgt ltPRICEgt10.90lt/PRICEgt ltYEARgt199
5lt/YEARgt lt/CDgt lt/CATALOGgt
29
Network Model
  • Built on hierarchical model but allows multiple
    parents and multiple children

30
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

31
Dr. Edgar F(rank) Codd
  • MA Mathematics, MA Chemistry
  • MS and PhD in Communication Sciences
  • ACM Turing Award (1981)

32
Tables?
  • Artists Table (Relation)?
  • ArtistID, City, Region, ... Columns
    (Attributes)?
  • Each row is called a Record (Tuple)?

33
Using Relational Databases and SQL
Part II Database Management Systems
34
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 informati
    on if the system fails.
  • Source Wikipedia

35
Database Management Systems (DBMS)?
  • Some common relational DBMSs
  • MySQL, PostgreSQL (free, open source)?
  • Oracle, MS SQL Server (commercial)?

36
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

37
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

38
Database Management Systems (DBMS)?
39
Using Relational Databases and SQL
Part III Query Languages
40
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

41
Query Languages
  • Data Sublanguage Alpha (Codds original query
    language)
  • Data Sublanguage SEQUEL (SQL)?

42
SQL
  • Stands for 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

43
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.

44
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, ...

45
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?

46
Using Relational Databases and SQL
Part IV Lyric Database Discussion
47
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

48
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
  • Lets go over all the tables and attributes

49
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!)

50
Using Relational Databases and SQL
Part V MySQL
51
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.

52
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
    dont need. Be careful to get the binaries
    instead. MySQL 5.5.8-win32, for example, is 132
    MB. The 27 MB file is the source code.

53
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 dont
    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

54
Mac Users
  • An OSX version of MySQL is available, but some
    students have had difficulties with it and I am
    not very good at supporting OSX.
  • If you find it hard to work with, I can give you
    an account on the cs1 server, which has MySQL.
  • You might also consider using the Windows version
    with Boot Camp or an emulator.

55
Using MySQL In Windows
  • 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 wont
    have to navigate there every time. However, you
    wont 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

56
Some MySQL Commands
  • Once MySQL has started and you see the mysql
    prompt
  • At mysqlgt prompt type in show databases
  • At mysqlgt prompt type in create database lyric
  • At mysqlgt prompt type in use lyric
  • At mysqlgt prompt type in show tables
  • You shouldnt see any yet

57
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 mysqlgt 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 mysqls bin directory,
    all you will have to type is source lyric.sql
  • You should see a bunch of messages like
    thisQuery OK, 1 rows affected (0.01 sec).

58
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
  • ---------------------------------------------
    ---------------
  • 1 Bob Bentley bbb
    100.00 4
  • 2 Lisa Williams lmw
    300.00 4
  • 3 Clint Sanchez cls
    100.00 1
  • 4 Scott Bull sjb
    NULL NULL
  • ---------------------------------------------
    ---------------
  • 4 rows in set (0.39 sec)

59
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
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