Chapter 1

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Chapter 1

Getting Started with MySQL

MySQL Developer's Library, Paul DuBois 4th Edition


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Why a database system?

• information you want to organize and manage is so voluminous or complex that your records.

• large corporations processing millions of transactions a day

• But even small-scale operations involving a single person maintaining information


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Database system - Scenarios

• Your carpentry business has several employees. You need to maintain employee and payroll records so that you know who you've paid and when, and you must summarize those records so that you can report earnings statements to the government for tax purposes. You also need to keep track of the jobs your company has been hired to do and which employees you've scheduled to work on each job.


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Database system - Scenarios

• You're a teacher who needs to keep track of grades and attendance. Each time you give a quiz or a test, you record every student's grade. It's easy enough to write down scores in a gradebook, but using the scores later is a tedious chore. You'd rather avoid sorting the scores for each test to determine the grading curve, and you'd really rather not add up each student's scores when you determine final grades at the end of the grading period. Counting each student's absences is no fun, either.


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Advantages of Electronically Maintained records

• Reduced record filing time• Reduced record retrieval time• Flexible retrieval order• Flexible output format• Simultaneous multiple-user access to records• Remote access to and electronic transmission

of records


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Sample Databases

• The organizational secretary scenario. Our organization has these characteristics: It's composed of people drawn together through an affinity for United States history (called, for lack of a better name, the U.S. Historical League). The members renew their membership periodically on a dues-paying basis. Dues go toward League expenses such as publication of a newsletter, "Chronicles of U.S. Past." The League also operates a small Web site; it hasn't been developed very much, but you'd like to change that.


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Sample Databases

• The grade-keeping scenario. You are a teacher who administers quizzes and tests during the grading period, records scores, and assigns grades. Afterward, you determine final grades, which you turn in to the school office along with an attendance summary.


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Banner Advertisement BusinessCompany TableCompany NameCpmpany_Num (PK)AddressPhone

Ad Table

Company_num (FK)

Ad_num (FK)

Hit Fee

Hit_table

Ad_num (FK)

date


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Mysql Installation

• Please see the word document Installing MySql 5


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Sample Database

• Please see appendix A for obtaining the sample database

• http://www.kitebird.com/mysql-book/


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Establishing Connection

• Start – All programs – mysql – mysql command line client

• From command prompt : – mysql -p -u root


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Executing MySql statements

• In the mysql command Line Client• Terminate all mysql statements with a ;– mysql> SELECT NOW(); – mysql> SELECT NOW(),

-> USER(), -> VERSION() -> ;

mysql waits for the statement terminator, you need not enter a statement all on a single line. You can spread it over several lines if you want


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Creating a database

• mysql> CREATE DATABASE sampdb; Create Database Statement + Name of the database

• mysql> USE sampdb; To select a database


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Create Tables

CREATE TABLE president (

last_name VARCHAR(15) NOT NULL, first_name VARCHAR(15) NOT NULL, suffix VARCHAR(5) NULL, city VARCHAR(20) NOT NULL, state VARCHAR(2) NOT NULL, birth DATE NOT NULL, death DATE NULL );


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Create tablesCREATE TABLE member (

member_id INT UNSIGNED NOT NULL AUTO_INCREMENT, PRIMARY KEY (member_id), last_name VARCHAR(20) NOT NULL, first_name VARCHAR(20) NOT NULL, suffix VARCHAR(5) NULL, expiration DATE NULL, email VARCHAR(100) NULL, street VARCHAR(50) NULL, city VARCHAR(50) NULL, state VARCHAR(2) NULL, zip VARCHAR(10) NULL, phone VARCHAR(20) NULL, interests VARCHAR(255) NULL

);


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Check structure of the table

• mysql> DESCRIBE president; • SHOW COLUMNS FROM president;• To view tables in the database– SHOW TABLES;

• To view databases on the server– Show databases;


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Grade Keeping ProjectCREATE TABLE students ( name VARCHAR(20) NOT NULL, sex ENUM('F','M') NOT NULL, student_id INT UNSIGNED NOT NULL AUTO_INCREMENT,

PRIMARY KEY (student_id) ) ENGINE = InnoDB;


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Grade Keeping Project

CREATE TABLE grade_event ( date DATE NOT NULL, category ENUM('T','Q') NOT NULL, event_id INT UNSIGNED NOT NULL AUTO_INCREMENT, PRIMARY KEY (event_id) ) ENGINE = InnoDB;


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Grade Keeping ProjectCREATE TABLE score ( student_id INT UNSIGNED NOT NULL, event_id INT UNSIGNED NOT NULL, score INT NOT NULL, PRIMARY KEY (event_id, student_id), INDEX (student_id), FOREIGN KEY (event_id) REFERENCES grade_event (event_id), FOREIGN KEY (student_id) REFERENCES students (student_id) ) ENGINE = InnoDB;


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Score table

• combination of the two columns a PRIMARY KEY ensures that we won't have duplicate scores for a student for a given quiz or test.

• combination of event_id and student_id that is unique.

• Foreign Key constraints - each student_id value in the score table must match some student_id value in the student table.


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Grade Keeping Project

CREATE TABLE absence ( student_id INT UNSIGNED NOT NULL, date DATE NOT NULL, PRIMARY KEY (student_id, date), FOREIGN KEY (student_id) REFERENCES students

(student_id) ) ENGINE = InnoDB;


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Storage Engine in Mysql• Default storage engine is MyISAM (indexed sequential access

method)• InnoDB offers "referential integrity" through the use of foreign

keys. • MySQL to enforce certain constraints on the interrelationships

between tables - important for the grade-keeping project tables:– Score rows are tied to grade events and to students: don't allow

entry of rows into the score table unless the student ID and grade event ID are known in the student and grade_event tables.

– Absence rows are tied to students: don't allow entry of rows into the absence table unless the student ID is known in the student table.

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INSERT data in the Tables• INSERT INTO tbl_name VALUES(value1,value2,...);

Example:• INSERT INTO students VALUES('Kyle','M',NULL);• INSERT INTO grade_event VALUES('2008-09-

03','Q',NULL); • the VALUES list must contain a value for each

column in the table, in the order that the columns are stored in the table.

• NULL values are for the AUTO_INCREMENT columns in the student and grade_event tables.



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INSERT data• insert several rows into a table with a single

INSERT statement by specifying multiple value lists:

• INSERT INTO tbl_name VALUES(...),(...),... ; Example:

• INSERT INTO students VALUES('Avery','F',NULL),('Nathan','M',NULL);

• Less typing than multiple INSERT statements, and more efficient for the server to execute.


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INSERT data• name the columns to which you want to assign

values, and then list the values• INSERT INTO member (last_name,first_name)

VALUES('Stein','Waldo'); • INSERT INTO students (name,sex)

VALUES('Abby','F'),('Joseph','M');


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Foreign Key Constraints with INSERT Data

• INSERT INTO score (event_id,student_id,score) VALUES(9999,9999,0);

• ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`sampdb`.`score`, CONSTRAINT `score_ibfk_1` FOREIGN KEY (`event_id`) REFERENCES `grade_event` (`event_id`))

• foreign key relationships prevent entry of bad rows in the score table.


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Adding data from a file

• Unzip the sample database• Copy and paste the following files in the data

directory – location may vary! C:\Documents and Settings\All Users\Application Data\MySQL\MySQL Server 5.1\

data\sampdb- president.txt- Student.txt- Member.txt- Score.txt- Absence.txt


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Adding data from a file

• mysql> source insert_president.sql; • Before running the below command– TRUNCATE TABLE member;

delete all data in the table

• LOAD DATA INFILE “member.txt” INTO TABLE member;

• LOAD DATA INFILE “president.txt” INTO TABLE president;


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Adding data from file

• Copy and paste the data from “insert_student” in Mysql command prompt to populate the student table– Insert_student file is in the unzipped sampdb

folder • Copy and paste the data from

“insert_grade_event” in Mysql command prompt to populate the grade_event table


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Adding data from file

• Copy and paste the data from “insert_score” in Mysql command prompt to populate the score table

• LOAD DATA INFILE “absence.txt” INTO TABLE absence;


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Sampdb Database

• You now have 6 tables in the Sampdb database and they have been populated

- Member- President- Student- Grade_event- Score- Absence


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Query

• To retrieve data from the database• SELECT * FROM president; – All data in the table president

• syntax of the SELECT statement is:SELECT what to retrieve FROM table or tables WHERE conditions that data must satisfy;


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Query

SELECT birth FROM president WHERE last_name = 'Eisenhower';

Retrieve data from one column SELECT name FROM student;

Data from 2 columns SELECT name, sex, student_id FROM student;


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Specifying Retrieval Criteria

SELECT * FROM score WHERE score > 95;


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string values

SELECT last_name, first_name FROM president WHERE last_name='ROOSEVELT';

SELECT last_name, first_name, birth FROM president

WHERE birth < '1750-1-1';


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Combination of Values

SELECT last_name, first_name, birth, state FROM president

WHERE birth < '1750-1-1' AND (state='VA' OR state='MA');


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Arithmetic Operators

+ Addition - Subtraction * Multiplication / Division DIV Integer division % Modulo (remainder after division)


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Comparison Operators

< Less than <= Less than or equal to = Equal to <=> Equal to (works even for NULL values) >or != Not equal to >= Greater than or equal to > Greater than


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Logical Operators

AND Logical AND OR Logical OR XOR Logical exclusive-OR NOT Logical negation


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Logical operators

SELECT last_name, first_name, state FROM president ->

WHERE state='VA' AND state='MA'; Empty set (0.36 sec)• Correct QuerySELECT last_name, first_name, state FROM

president WHERE state='VA' OR state='MA';

MySql Developers Library, Paul Dubois 4th Edition

Null and Not Null Queries

• SELECT last_name, first_name FROM president WHERE death IS NULL;

• SELECT last_name, first_name, suffixFROM president WHERE suffix IS NOT NULL;


Sorting Queries

• SELECT last_name, first_name FROM president ORDER BY last_name;

• SELECT last_name, first_name FROM president ORDER BY last_name DESC;


Sorting

• SELECT last_name, first_name, state FROM presidentORDER BY state DESC, last_name ASC;


Sorting – If condition

• SELECT last_name, first_name, death FROM presidentORDER BY IF(death IS NULL,0,1), death DESC;

• IF() evaluates to 0 for NULL values and 1 for non-NULL values.

• This places all NULL values ahead of all non-NULL values.


Limiting Query Results

• SELECT last_name, first_name, birth FROM president ORDER BY birth LIMIT 5;

• SELECT last_name, first_name, birth FROM presidentORDER BY birth DESC LIMIT 5;


Limiting Query Results

• SELECT last_name, first_name, birth FROM presidentORDER BY birth DESC LIMIT 10, 5;

• returns 5 rows after skipping the first 10


Random

• SELECT last_name, first_name FROM presidentORDER BY RAND() LIMIT 1;

• SELECT last_name, first_name FROM president ORDER BY RAND() LIMIT 3;


Concat Function

• SELECT CONCAT(first_name,' ',last_name),CONCAT(city,', ',state)FROM president;


Using Alias - As

• SELECT CONCAT(first_name,' ',last_name) AS Name, CONCAT(city,', ',state) AS BirthplaceFROM president;


Dates

• SELECT * FROM grade_event WHERE date = '2008-10-01';

• SELECT last_name, first_name, death FROM president WHERE death>='1970-01-01' AND death<'1980-01-01';


Functions Year(), Month(), dayofmonth()

• SELECT last_name, first_name, birthFROM president WHERE MONTH(birth) = 3;

• SELECT last_name, first_name, birthFROM presidentWHERE MONTHNAME(birth) = 'March';


Functions Year(), Month(), dayofmonth()

SELECT last_name, first_name, birthFROM president WHERE MONTH(birth) = 3 AND DAYOFMONTH(birth) = 29;


Date Calculations

• SELECT last_name, first_name, birth, death,TIMESTAMPDIFF(YEAR, birth, death) AS age FROM president WHERE death IS NOT NULL ORDER BY age DESC LIMIT 5;


Date Calculations – Add date

• SELECT DATE_ADD('1970-1-1', INTERVAL 10 YEAR);

• SELECT last_name, first_name, deathFROM president WHERE death>=“1970-1-1”AND death < DATE_ADD(“1970-1-1”, INTERVAL 10

YEAR);


Pattern matching

• SELECT last_name, first_name FROM president WHERE last_name LIKE 'W%';


summaries

• SELECT DISTINCT state FROM president ORDER BY state;

• Use the DISTINCT keyword to remove duplicate rows from a result.


summaries

• SELECT COUNT(*) FROM member; • COUNT(*) tells you the number of rows in

your table.• SELECT COUNT(*) FROM grade_event WHERE

category = 'Q';


summaries

• SELECT sex, COUNT(*) FROM student GROUP BY sex;

• SELECT state, COUNT(*) AS count FROM presidentGROUP BY state ORDER BY count DESC;


Queries – Multiple Tables

• SELECT student_id, date, score, category FROM grade_event INNER JOIN score ON grade_event.event_id = score.event_idWHERE date = '2008-09-23';


Queries – Multiple Tables

• SELECT student.name, grade_event.date, score.score, grade_event.category FROM grade_event INNER JOIN score INNER JOIN student ON grade_event.event_id = score.event_id AND score.student_id = student.student_idWHERE grade_event.date = '2008-09-23';


Queries – Multiple Tables and Functions

• SELECT grade_event.date, student.sex, COUNT(score.score) AS count, AVG(score.score) AS averageFROM grade_event INNER JOIN score INNER JOIN studentON grade_event.event_id = score.event_id AND score.student_id = student.student_id GROUP BY grade_event.date, student.sex;


Subquery

• SELECT last_name, first_name, birth FROM presidentWHERE birth < (SELECT birth FROM presidentWHERE last_name = 'Jackson' AND first_name = 'Andrew');


Delete Data

• DELETE FROM tbl_name WHERE which rows to delete;