Databases and PHPCreating and Using Databases in

mySQL

Database Basicsl Remember our Database goal:

l To organize some data in a manner that makes it easy to relate, store, and retrieve the data

Database Basicsl What do we need to know about databases?

l How to design a database -- last lecturel How to use and update a database -- this lecture

Database BasicsCreating a DatabaseUsing/Updating a Database

Basic SQL Commandsl Structured Query Language (SQL) is an

ANSI (American National Standards Institute) standard.

l SQL is a �language� for creating, modifying, and deleting database tables, records, and fields.

l Many different databases use SQLl Most databases have proprietary extensions

of SQL.

Basic SQL Commandsl SQL allows you to:

l access a databasel execute queries against a databasel retrieve data from a databasel Insert, Update and Delete records from a

database.

SQL Tablesl Everything in SQL is stored in tables: Each table is identified by a

name (i.e. �People"). Tables contain records (rows) with data.l Below is an example of a table called "People":

The table contains three records (one for each person) and four columns (LName, FName, Phone, and ID).

Lname Fname Phone# IDSmith John 5309 0Karlsson Karl 4200 1Wallace William 8569 2

Basic SQL DML (data manipulation language)Command Action

CREATE Creates a new table.

USE Use a database

DESCRIBE Show the fields in a table.

ALTER Modifies the definition (structure, data types, etc.) of an existing table.

DROP Permanently removes elements such as tables and fields.

INSERT Adds a record to a table.

LOAD DATA Loads records from a text file.

UPDATE Modifies data in an existing record.

SELECT Performs a query on a table, including mathematical functions, field comparison, pattern matching, etc.

SHOW Print the databases (or tables or grants) available.

DELETE Permanently removes elements from a table.

Basic SQL Commandsl Syntax

l Commands are by convention in all capital letters. Doesn�t really matter.

l Every command ends with a semicolon (�;�)l Table and field capitalization does matter.

Using mySQL directly (no php)l First must log into the Linux server using ssh

or putty.l Then must start mySQL:

mysql -u yourAccountName -pl Where yourAccountName is, well, your account

namel Note that everything is lower casel The mySQL admin has given you access to a

particular database.l You will be prompted for a password.

Using mySQL directly (no php)l SHOW

l To see what databases you have access to type:mysql> SHOW DATABASES;

+-----------+| Database |

+-----------+

| Ithaca |

| test |+-----------+

2 rows in set (0.00 sec)

l Here, accountName has access to the Ithacadatabase and a test database

Using mySQL directly (no php)l To see what tables are in your database, type:

mysql> SHOW TABLES FROM Ithaca;+--------------------+| Tables_in_students |+--------------------+| student || courses || instructors || students_courses |+--------------------+1 row in set (0.02 sec)

mysql>

l Note that the database is specified: Ithacal Here, the students database has four tables named student,

courses, instructors, and students_courses. l Caution: capitalization matters in the name of the database!

Using mySQL directly (no php)l To see what privileges you have, type:

mysql> SHOW GRANTS FOR cs205user@localhost;+--------------------------------------------------------------------------------------+| GRANTS for cs205@localhost |+--------------------------------------------------------------------------------------+| GRANT USAGE ON *.* TO 'cs205'@'localhost' IDENTIFIEDY BY PASSWORD '032c41e84373a7' || GRANT SELECT, INSERT, DELETE, CREATE ON 'Ithaca'.* TO 'cs205user'@'localhost' |+--------------------------------------------------------------------------------------+2 rows in set (0.02 sec)

mysql>

l The localhost means the computer you are logged into.l You can also have privileges when sending commands from a remote

machine. In this case you may see '%' or an IP address instead of localhost

l USAGE means no permissions. l The 'Ithaca'.* is the database Ithaca

Add a userl Log in as root using the root passwordl CREATE USER ‘barrg’@’localhost’

IDENTIFIED BY ‘ithaca’l GRANT ALL PRIVILEGES ON *.* to

'barrg'@'localhost’;

Modify a userl To change a user’s password:ALTER USER 'userName'@'localhost' IDENTIFIED BY 'New-Password-Here’;

l To add privileges (e.g., ALL PRIVILEGES):GRANT type_of_permission ON ‘database_name.table_name’.* TO ‘username’@'localhost’;

l To revoke privileges:REVOKE type_of_permission ON ‘database_name.table_name’.* FROM ‘username’@‘localhost’

CREATE a databasel CREATE

l Allows you to create new databases and tables, depending upon the permissions you have.

l Syntax to create a database:

CREATE DATABASE Junk;

Note! The square brackets indicate optional items. Do NOT put the brackets in your command!

Using mySQL directly (no php)l USE.

l To automatically use a particular database for all your work:mysql> USE Ithaca;Reading table information for completion of table and column

namesYou can turn off this feature to get a quicker startup with

-A

Database changed

mysql>

l Now you can enter commands without specifying the database:mysql> SHOW TABLES;

CREATE a tablel CREATE

l Allows you to create new databases and tables, depending upon the permissions you have.

l You specify the fields of the table (can modify later), but not the values of the fields.

l Syntax to create a table:CREATE TABLE [table name][(name_of_field1

field1_datatype, name_of_field2 field2_datatype , …)] [options ];

Note! The square brackets indicate optional items. Do NOT put the brackets in your command!

Basic SQL commandsl CREATE

l Example: creating the instructors table CREATE TABLE instructors(instructorID int not null primary key,instrName varchar (30) not null);l Notice the typel Not null means that the field is not initialized to a default value

automatically.§ If you leave this off, then a default value will be used when a new record is

created (if a value is not provided).§ The actual default value varies depending on the type§ Eg, ints are by default 0

You can leave the not null and primary key off of every line!

not null means that field MUST have a valueprimary key is a unique identifier for the row. Every value must be unique.

Basic SQL commandsl CREATE

l Example: creating the instructors table CREATE TABLE instructors(instructorID int not null primary key,instrName varchar (30) not null);l Varchar(20) means that the field will have a varying number of

characters up to 20 maxl More information about CHAR and VARCHAR is here:

§ http://dev.mysql.com/doc/refman/5.0/en/char.htmll Information about other types is at:

§ http://dev.mysql.com/doc/refman/5.0/en/data-types.html

Basic SQL commandsmysql> SHOW TABLES;+-------------------+| Tables_in_Ithaca |+-------------------+| student || courses || instructors || students_courses |+-------------------+

2 rows in set (0.00 sec)

mysql> CREATE TABLE clubs (-> studentID int primary key,-> clubName varchar(20) not null-> );

Query OK, 0 rows affected (0.00 sec)

mysql> SHOW TABLES;+-------------------+| Tables_in_Ithaca |+-------------------+| student || courses || instructors || students_courses || clubs |+-------------------+

3 rows in set (0.00 sec)

Create a student table with fields first, last, ID, major

ID is an int, a primary key and not nullfirst, last are varchar(20)

Create a student table with fields first, last, ID, depart

ID is an int, a primary key and not nullfirst, last are varchar(20)

Basic SQL commandsl DESCRIBE

l Allows you to see the format of the fields in a table.l Example: to see the fields in the Students table:

mysql> DESCRIBE student; +--------------+--------------+------+-----+---------+-------+| Field | Type | Null | Key | Default | Extra |+--------------+--------------+------+-----+---------+-------+| firstname | varchar(20) | YES | | | || lastname | varchar(20) | YES | | | || GPA | decimal(3,2) | YES | | 0.00 | || phone | varchar(15) | YES | | | || major | varchar(30) | YES | | | || dorm | varchar(20) | YES | | | || creditsTaken | decimal(3,0) | YES | | 0 | || studentID | decimal(6,0) | NO | | | |+--------------+--------------+------+-----+---------+-------+7 rows in set (0.00 sec)

mysql>

Basic SQL commandsl SHOW

l You can see all the databases that you have access to:SHOW DATABASES;

l You can also see the tables that are in a database:USE Ithaca;

SHOW TABLES;

Basic SQL commandsl ALTER

l Allows you to modify elements of a particular table.

l Can add fields, change field types, delete fields.l Example: to change the field size of name:

ALTER TABLE courses CHANGE InstructorID InstructorID VARCHAR(30);

l Example: to add a column to a table:ALTER TABLE courses ADD days varchar(5);

ALTERl Change the student table to include GPA, an

int.

Basic SQL commandsl DROP

l Allows you to delete an entire tableDROP TABLE [table name];

l Example:DROP TABLE Students;

l Also can use to delete specific fields:ALTER TABLE courses DROP descript;

Where courses is a table and descript is a field

Basic SQL commandsl INSERT

l Allows you to add a record to a tableINSERT INTO [table name]([name of field1] , [name

of field2] , …) VALUES (�[value of field 1]� , �[value of field 2]� , … );

l Syntax:l Must use single or double quotes around your values.l Convention is to use single quotes, but it doesn�t matter.

Note! The square brackets indicate optional items. Do NOT put the brackets in your command!

Basic SQL commandsl INSERT

l Example:

mysql> INSERT INTO student (firstname, lastname, GPA, phone, major, dorm, creditsTaken) -> VALUES ('John', 'Smith', '3.6', '274-3948', 'CS', 'Stanton', '63');

Query OK, 1 row affected (0.05 sec)

mysql> SELECT * FROM student;+-----------+----------+------+----------+-------+---------+--------------+| firstname | lastname | GPA | phone | major | dorm | creditsTaken |+-----------+----------+------+----------+-------+---------+--------------+| John | Smith | 3.60 | 274-3948 | CS | Stanton | 63 |+-----------+----------+------+----------+-------+---------+--------------+1 row in set (0.00 sec)

mysql>

INSERTl Insert 2 records into the students table l and 2 records into the instructors table

Basic SQL commandsl DELETE

l Allows the deleting of records from tables :DELETE FROM [table name] WHERE [expression];

l Example: to delete all records with instructorID of 76765 from the courses table:DELETE FROM courses WHERE instructorID = �76765�;

l If you want to delete only the record where the instructor ID is 76765 and the course is 304-212, then use:DELETE FROM courses WHERE instructorID = �76765�AND courseID = �304-212�;

Note! The square brackets indicate optional items. Do NOT put the brackets in your command!

Basic SQL commandsl DELETE

l If you leave out the WHERE expression, you delete all records!DELETE FROM courses;

Deletes all the records in the courses table.l If you want to delete a specific field from all records, use

the ALTER command:ALTER TABLE courses DROP instructorID;

Basic SQL commandsl UPDATE

l Modifies part of a record without replacing the entire record:UPDATE [table name]SET [field name] = �[new value]� WHERE [expression];

l Example: change name of instructor for course 304-212:UPDATE courses SET InstructorID = �49281� WHERE courseID = �304-212�;

l Syntax:l If you leave out the WHERE, then all records are updated!l You can perform string functions and math functions on existing records

and use the UPDATE command to modify their values

Note! The square brackets indicate optional items. Do NOT put the brackets in your command!

UPDATEl Change the GPA of a student

SQL Queriesl SELECT

l This is the command you use to see what�s in your database.l When talking about databases, a SELECT is called a �query�

l Causes certain records in your table to be chosen, based on criteria that you define:SELECT [field names] FROM [table name] WHERE [expression]

ORDER BY [fields];

l Example: to select all the records in a table:SELECT * FROM courses;

l Example: to select just the entries in the courseID field of the courses table:SELECT courseID FROM courses;

SQL Queries: WHEREl You can use the word WHERE to limit your result sets, using

the following operators:= equal to<> Not equal to>, <, <= GT, LT, LTEBETWEEN in a specified rangeLIKE matches a pattern

SELECT description FROM courses WHERE courseID = �COMP 207�;

returns+-------------+| description |+-------------+| Game Dev | +-------------+1 row in set (0.00 sec)

AND, ORl AND and OR can also be used to construct more complicated queries:

SELECT * FROM People WHERE id > 0 AND Lname LIKE �Hoch�

l The * is used as a wildcard, and will return the data in all columns

l LIKE means only Lnames that exactly match �Hoch� will be returned

l If you want Lnames that begin with �Hoch�, must use a wildcard:

Lname LIKE �Hoch%�

l The % will match 0 or more characters, the underscore �_� will match

exactly 1 character.

l To match the �%� or �_� character, backslash them: �\%� or �\_�

AND, ORl AND and OR can also be used to construct more complicated queries:

mysql> SELECT * FROM courses WHERE instructorID = 343434 AND room = 'Williams 309';+----------+-------------+--------------+------+---------+--------------+| courseID | description | instructorID | days | time | room |+----------+-------------+--------------+------+---------+--------------+| COMP 122 | Legos | 343434 | TR | 11:00am | Williams 309 | | COMP 123 | Legos II | 343434 | R | 2:30pm | Williams 309 | +----------+-------------+--------------+------+---------+--------------+2 rows in set (0.00 sec)

mysql>

SQL Queriesl SELECT

l To select all records and have them returned in a particular order, use an expression for ORDER BY.

l Example: to view courseID and course Descript ordered by courseID from smallest to largest:SELECT courseID, description FROM courses ORDER BY courseID DESC;

l DESC means descending. ASC means ascending (ASC is the default)

SQL query, orderedmysql> SELECT courseID, description FROM courses ORDER BY courseID;+----------+-------------+| courseID | description |+----------+-------------+| COMP 110 | Intro | | COMP 122 | Legos | | COMP 123 | Legos II | | COMP 171 | CS I | | COMP 190 | MatLAB | | COMP 205 | Adv Web | | COMP 207 | Game Dev | | COMP 210 | Org | | COMP 310 | Op Sys | | COMP 315 | Graphics | | COMP 375 | DB | | COMP 390 | AI | +----------+-------------+12 rows in set (0.00 sec)

mysql>

SQL Queriesl SELECT

l Can also perform mathematical and string functions within SQL statements. To count the number of courses:SELECT COUNT(courseID) FROM courses;

l Use the WHERE option to specify certain field values.l Example: get course ID and description for all courses

taught by the instructor with ID 76765:SELECT courseID, descript FROM courses WHERE InstructorID = �76765�;

SQL Queriesl SELECT

l Can select fields from different tables :SELECT courses.descript, instructors.instructorName FROM courses, instructors WHERE courses.InstructorID = instructors.InstructorID;

l This query searches the instructors table and the courses table.l When the instructor ID in the instructors table matches the

instructor ID in the courses tablel Then the corresponding course description from the courses

table and the corresponding instructor name from the instructors table are printed.

SQL query, multiple tablesmysql> SELECT courses.description, instructors.lastname FROM courses, instructors

-> WHERE courses.instructorID = instructors.instructorID;+-------------+------------+| description | lastname |+-------------+------------+

| CS I | Applin | | Adv Web | Barr | | MatLAB | Erkan | | DB | Woodworth | | Graphics | Stansfield |

| AI | Zollo | | Org | Daehn | | Legos | Woodworth | | Intro | Woodworth | | Game Dev | Stansfield |

| Op Sys | Barr | | Legos II | Woodworth | +-------------+------------+12 rows in set (0.03 sec)

mysql>

Complex SQL querymysql> SELECT instructors.lastname FROM instructors, student, courses, students_courses

WHERE student.studentID = 222222 AND students_courses.studentID = student.studentID AND students_courses.courseID = courses.courseID AND courses.instructorID = instructors.instructorID;

+------------+| lastname |+------------+| Applin | | Stansfield | | Woodworth | +------------+27 rows in set (0.00 sec)

Must specify which

lastname since several

tables have this field

Must specify all

tables that will

be used in the

query

Must specify

every table

Notes:

1. Every table that you use in the SELECT or WHERE

clauses must be named in the FROM clause.

2. In the WHERE clause, each AND clause should

further restrict your search.

Complex SQL querymysql> SELECT instructors.lastname FROM instructors, student, courses, students_courses

WHERE student.studentID = 222222 AND students_courses.studentID = student.studentIDAND students_courses.courseID = courses.courseID AND courses.instructorID = instructors.instructorID;

+-----------+----------+------+--------------+-------+--------+--------------+-----------+| firstname | lastname | GPA | phone | major | dorm | creditsTaken | studentID |+-----------+----------+------+--------------+-------+--------+--------------+-----------+| George | Smith | 3.20 | 607-274-1234 | CS | Pepsi | 37 | 111111 | | Sally | Jones | 4.00 | 607-274-2345 | CS | Coke | 56 | 222222 || Fred | Kelly | 2.30 | 607-274-3456 | CIS | Dew | 48 | 333333 | | Ashley | Nevins | 3.80 | 607-274-4567 | CIS | Pepper | 101 | 444444 | | Mike | Melville | 3.90 | 607-274-5678 | CIS | Orange | 59 | 555555 | | Coleen | Richford | 2.80 | 607-274-6789 | CS | Pepper | 121 | 666666 | | Samantha | Foley | 3.50 | 607-274-7891 | CS | Pepper | 133 | 777777 | | Cynthia | James | 2.70 | 607-274-8912 | CIS | Coke | 76 | 888888 | | Sam | Smalley | 2.10 | 607-274-9123 | CIS | Orange | 92 | 999999 | +-----------+----------+------+--------------+-------+--------+--------------+-----------+

1. Restrict to studentID 222222

+-----------+----------+| studentID | courseID |+-----------+----------+| 111111 | COMP 310 | | 111111 | COMP 122 | | 111111 | COMP 375 | | 111111 | COMP 390 | | 222222 | COMP 171 | | 222222 | COMP 207 | | 222222 | COMP 122 || 333333 | COMP 310 |

2. The clause students_courses.studentID = student.studentID restricts us to using only the rows in the students_courses table where studentID is 222222

Complex SQL querymysql> SELECT instructors.lastname FROM instructors, student, courses, students_courses

WHERE student.studentID = 222222 AND students_courses.studentID = student.studentID AND students_courses.courseID = courses.courseID AND courses.instructorID = instructors.instructorID;

+-----------+----------+| studentID | courseID |+-----------+----------+| 111111 | COMP 310 | | 111111 | COMP 122 | | 111111 | COMP 375 | | 111111 | COMP 390 | | 222222 | COMP 171 | | 222222 | COMP 207 | | 222222 | COMP 122 || 333333 | COMP 310 |

3. Now the clause students_courses.courseID = courses.courseID restrict the rows in the courses table to the values �COMP 171�, �COMP 207�, and �COMP 122�

+----------+-------------+--------------+------+---------+--------------+| courseID | description | instructorID | days | time | room |+----------+-------------+--------------+------+---------+--------------+| COMP 171 | CS I | 676767 | MWF | 9:00am | Williams 303 | | COMP 205 | Adv Web | 121212 | MWF | 10:00am | Williams 309 | | COMP 190 | MatLAB | 232323 | M | 4:00pm | Williams 303 | | COMP 375 | DB | 343434 | MWF | 2:00pm | Williams 303 | | COMP 315 | Graphics | 454545 | MWF | 11:00am | Williams 309 | | COMP 390 | AI | 565656 | MWF | 10:00am | Williams 303 | | COMP 210 | Org | 787878 | TR | 10:00am | Williams 309 | | COMP 122 | Legos | 343434 | TR | 11:00am | Williams 309 | | COMP 110 | Intro | 343434 | T | 2:30pm | Williams 319 | | COMP 207 | Game Dev | 454545 | MWF | 4:00pm | Williams 303 | | COMP 310 | Op Sys | 121212 | MWF | 8:00am | Williams 309 | | COMP 123 | Legos II | 343434 | R | 2:30pm | Williams 309 | +----------+-------------+--------------+------+---------+--------------+

Complex SQL querymysql> SELECT instructors.lastname FROM instructors, student, courses, students_courses

WHERE student.studentID = 222222 AND students_courses.studentID = student.studentID AND students_courses.courseID = courses.courseID AND courses.instructorID = instructors.instructorID;

+-----------+------------+---------------+--------------+------+--------------+-----------------+| firstname | lastname | office | phone | dept | instructorID | email |+-----------+------------+---------------+--------------+------+--------------+-----------------+| John | Barr | Williams 401A | 607-274-9876 | CS | 121212 | barr@ithaca | | Ali | Erkan | Williams 401B | 607-274-8765 | CS | 232323 | erkan@ithaca | | Pat | Woodworth | Williams 401D | 607-274-7654 | CS | 343434 | woodwrth@ithaca | | Sharon | Stansfield | Williams 301D | 607-274-6543 | CS | 454545 | stansfield@itha | | Teresa | Zollo | Williams 301C | 607-274-5432 | CS | 565656 | zollo@ithaca | | Anne | Applin | Williams 301C | 607-274-4321 | CS | 676767 | applin@ithaca | | Jim | Daehn | Williams 309 | 607-274-3219 | CS | 787878 | daehn@ithaca | +-----------+------------+---------------+--------------+------+--------------+-----------------+

4. Since we can only use the columns in the courses table that have been chosen (shown in red), the clause courses.instructorID =

instructors.instructorID will only choose the lines 676767, 343434, and 454545 from the instructors table.

+----------+-------------+--------------+------+---------+--------------+| courseID | description | instructorID | days | time | room |+----------+-------------+--------------+------+---------+--------------+| COMP 171 | CS I | 676767 | MWF | 9:00am | Williams 303 | | COMP 205 | Adv Web | 121212 | MWF | 10:00am | Williams 309 | | COMP 190 | MatLAB | 232323 | M | 4:00pm | Williams 303 | | COMP 375 | DB | 343434 | MWF | 2:00pm | Williams 303 | | COMP 315 | Graphics | 454545 | MWF | 11:00am | Williams 309 | | COMP 390 | AI | 565656 | MWF | 10:00am | Williams 303 | | COMP 210 | Org | 787878 | TR | 10:00am | Williams 309 | | COMP 122 | Legos | 343434 | TR | 11:00am | Williams 309 | | COMP 110 | Intro | 343434 | T | 2:30pm | Williams 319 | | COMP 207 | Game Dev | 454545 | MWF | 4:00pm | Williams 303 | | COMP 310 | Op Sys | 121212 | MWF | 8:00am | Williams 309 | | COMP 123 | Legos II | 343434 | R | 2:30pm | Williams 309 | +----------+-------------+--------------+------+---------+--------------+

Complex SQL querymysql> SELECT instructors.lastname FROM instructors, student, courses, students_courses

WHERE student.studentID = 222222 AND students_courses.studentID = student.studentID AND students_courses.courseID = courses.courseID AND courses.instructorID = instructors.instructorID;

+-----------+------------+---------------+--------------+------+--------------+-----------------+| firstname | lastname | office | phone | dept | instructorID | email |+-----------+------------+---------------+--------------+------+--------------+-----------------+| John | Barr | Williams 401A | 607-274-9876 | CS | 121212 | barr@ithaca | | Ali | Erkan | Williams 401B | 607-274-8765 | CS | 232323 | erkan@ithaca | | Pat | Woodworth | Williams 401D | 607-274-7654 | CS | 343434 | woodwrth@ithaca | | Sharon | Stansfield | Williams 301D | 607-274-6543 | CS | 454545 | stansfield@itha | | Teresa | Zollo | Williams 301C | 607-274-5432 | CS | 565656 | zollo@ithaca | | Anne | Applin | Williams 301C | 607-274-4321 | CS | 676767 | applin@ithaca | | Jim | Daehn | Williams 309 | 607-274-3219 | CS | 787878 | daehn@ithaca | +-----------+------------+---------------+--------------+------+--------------+-----------------+

5. Now when we choose a lastname in instructors.lastname we can only choose the names in the table that have been selected (highlighed in red below) by the WHERE clause.

+------------+| lastname |+------------+| Applin | | Stansfield | | Woodworth | +------------+

Basic SQL commandsl LOAD DATA

l Allows you to loading record data from a filel Technique:

l Create a file using any text editor.l Each record, consisting of all the columns in the table,

must be on its own line.l Separate each column by a Tab character.l You can leave a column blank for a particular record

by placing a �\n� in that column for the record.l Any blank lines you leave in the file result in blank

lines in the database table.

Basic SQL commandsl LOAD DATA

l To insert data into a table from a file:LOAD DATA LOCAL INFILE �/myDir/myfile.txt� INTO

TABLE tableName;

Syntax:l Must use single or double quotes around your file name.l Either enter the full path to the file or have it in the directory

where you were when you started the mysql command.

Basic SQL commandsl LOAD DATA

l Example: Assume that you started mysql from a directory which contains the file students.txt

l You can load the information from this file into the students table of the Ithaca DB with:

USE Ithaca;LOAD DATA LOCAL INFILE �students.txt� INTO TABLE

tableName;

SQL Resourcesl For more info on SQL I�d recommend the

following sites:

l http://dev.mysql.com/doc/l http://www.w3schools.com/sql/l webmonkey.coml PHP.Net