databaseMysqlphp MySQL DBMS MySQL DBMS.ppt

LIS651 lecture 2
databases,
mySQL and PHP mySQL functions
Thomas Krichel
2008-11-08

today
• Today I talk about
– arrays and table (again, since this causes problems)
– some basic mySQL commands
– a PHP interface to mySQL called mysqli
• Today you do
– create a table with phpmyadmin
– write PHP scripts to read/write data to the table using
the web

databases
• Databases are collection of data with some
organization to them.
• The classic example is the relational database.
• But not all database need to be relational
databases.

relational databases
• A relational database is a set of tables. There
may be relations between the tables.
• Each table has a number of record. Each record
has a number of fields.
• When the database is being set up, we fix
– the size of each field
– relationships between tables

problem with this database
• All data wrong, but this is just for illustration.
• Name covered inconsistently. There is no way to
find films by Woody Allan without having to go
through all spelling variations.
• Mistakes are difficult to correct. We have to
wade through all records, a masochist’s
pleasure.

Better movie database
ID | title | director | year
M1| Gone with the wind | D1 | 1963
M2| Room with a view | D1 | 1985
M3| High Noon | D2 | 1974
M4 | Star Wars | D3 | 1993
M5| Alien | D2 | 1987
M6| Blowing in the Wind | D3 | 1962
ID | director name | birth year
D1 | Ford Coppola, Francis| 1942
D2 | Allan, Woody | 1957
D3 | Spielberg, Steven | 1942

Relational database
• We have a one to many relationship between
directors and film
– Each film has one director
– Each director has produced many films
• Here it becomes possible for the computer
– To know which films have been directed by Woody
Allen
– To find which films have been directed by a director
born in 1942

Many-to-many relationships
• Each film has one director, but many actors star
in it. Relationship between actors and films is a
many to many relationship.
• Here are a few actors
ID | sex | actor name | birth year
A1 | f | Brigitte Bardot | 1972
A2 | m | George Clooney | 1927
A3 | f | Marilyn Monroe | 1934

Actor/Movie table
actor id | movie id
A1 | M4
A2 | M3
A3 | M2
A1 | M5
A1 | M3
A2 | M6
A3 | M4
… as many lines as required

databases in libraries
• Relational databases dominate the world of
structured data
• But not so popular in libraries
– Slow on very large databases (such as catalogs)
– Library data has nasty ad-hoc relationships, e.g.
• Translation of the first edition of a book
• CD supplement that comes with the print version
Difficult to deal with in a system where all relations and
field have to be set up at the start, can not be changed
easily later.

databases in web sites
• Lots of active web sites are driven by relational
databases. All large active web sites are.
• The design of a active web site first involves
looking at databases.
• In a shop situation, we have the following tables
– customers
– products
– orders
– orders_products
for multiple to multiple relationship between orders and products.

SQL
• SQL, also pronounced sequel, stands for
"structured query language".
• It is a standard language for querying database.
• In database speak a query is anything one can do
to a database.

casing and colon
• Traditionally SQL commands are written with
uppercase.
• mySQL commands are really case-insensitive.
• But variable names in the commands are case-
sensitive. I will therefore write them in lowercase.
• All SQL statements are ended with a semicolon.

mySQL
• They are a very successful, open-source vendor
of SQL software.
• Their product is basically freely available.
• We will learn the mySQL dialect of SQL.

phpmyadmin
• phpmyadmin is a set of PHP scripts that create a
general purpose interface to work with a mySQL
database.
• It is written in PHP.
• It lives at http://wotan.liu.edu/phpmyadmin.
• You need an account. This is not your wotan
account, but a permission to use a database on
the mySQL server running at wotan.

using mySQL
• mySQL server is installed on wotan.
• It is a daemon that deals with client requests.
• There is also a tty client installed. To use it you
log into wotan and type
mysql -u user -p
and then you type in your password.
• We will cover this in the last lecture.

CREATE DATABASE
• CREATE DATABASE a mySQL command to
create a new database.
• Example
CREATE DATABASE newbase;
• creates a database newbase.
• You have no privileges to create a database.
• But I don’t see the reason you wanting to do that.

creating mySQL databases
• To create a user account for your, I did
CREATE DATABASE user_name;
• user_name is your user name. It is the name of
your database as well as the name under which
you are logging in.

USE
• USE database; tells mySQL to start working with
the database database.
• If you have not issued a USE command, you can
still address a table table by using database.table,
where datebase is the name of your database
and table is the name of your table. You are using
the dot to link the two together.

GRANT
• This is a command to create users and give them
privileges. A simplified general syntax is
GRANT privileges ON item TO user_name
[IDENTIFIED BY 'password'] [WITH GRANT OPTION]
• If you use WITH GRANT OPTION, you allow the
user to grant other users the privileges that you
have given to her.

user privileges I
• SELECT allows users to select (read) records
from tables. Generally select is a word used for
read in databases.
• INSERT allows users to insert new rows into
tables.
• UPDATE allows users to change values in
existing table rows.
• DELETE allows users to delete table rows
(records)
• INDEX allows user to index tables

user privileges II
• ALTER allows users to change the structure
of the database.
– adding columns
– renaming columns or tables
– changing the data types of tables
• DROP allows users to delete databases or
tables. In general, the word drop refers to deleting
database or tables.

user privileges III
• CREATE allows users to create new databases
or tables. If a specific table or database is
mentioned in the GRANT statement, users can
only create that database or table, which will
mean that they have to drop it first.
• USAGE allows users nothing. This is a useful
point to start with if you just want to create a user.

creating mySQL databases
• To allow you access to your databases, I did
GRANT ALL ON user_name.* TO user_name
IDENTIFIED BY 'secret_word' WITH GRANT OPTION;
• user_name is your user name. It is the name of
your database as well as the name under which
you are logging in.
• 'secret_word' is the secret word we use for the
quizzes.

REVOKE
• This is the opposite of GRANT.

create a web user
• You do not want to give the same access rights to
people coming in from the web as you have.
• You do not want to do this. You personally have
too many privileges.
• I have yet to find out how you can create a web
user by yourself.

creating tables
• This is done conveniently in phpmyadmin.
• Here is an example for real SQL code
CREATE TABLE customers (customer_id INT UNSIGNED
NOT NULL AUTO_INCREMENT PRIMARY KEY, name
CHAR(50) NOT NULL, address CHAR(100) NOT NULL,
email CHAR(40), state CHAR(2) NOT NULL);

column data types
• TINYINT can hold a number between -128 and
127 or between 0 to 255. BIT or BOOL are
synonyms for the TINYINT.
• SMALLINT can hold a number between -32768
and +32767 or 0 and 65535
• INT can hold a number between -2**31 and
2**31-1 or between 0 and 2**32-1. INTEGER is a
synonym for INT.
• BIGINT can hold a number between -2**63 and
2**61-1 or between 0 and 2**64-1.

column data types: float
• FLOAT is a floating number on 4 bytes
• DOUBLE is a floating number on 8 bytes
• DECIMAL(x,y) where x is the number of digits
before the decimal point and y is the number of
digits after the decimal point.

column data types: dates
• DATE is a day from 1000-01-01 to 9999-12-31.
• TIME is a time from -838:59:59 to 838:59:59
• DATETIME is a date and time, usually displayed
as YYYY-MM-DD HH:MM:SS
• However, the easiest way I find is to store a date
as as INT.

date as an INT
• The UNIX time stamp is the number of seconds
from the 1st
of January 1970.
• The current value is returned by the PHP function
time().
• All values can be converted by the PHP funcition
date() function into strings that humans can easily
understand. Please refer to the help page
http://php.net/manual/en/function.date.php to see
the formating option.

field options
• PRIMARY KEY says that this column is a the
primary key. There can be only one such column.
Values in the column must be unique.
• AUTO_INCREMENT can be used on columns
that contain integer values.
• NOT NULL requires the field not to be empty.

addressing database tables
columns
• Let there by a database database with a table
table and some column column. Then it is
addressed as database.table.column.
• Parts of this notation can be left out if it is clear
what is meant, for example if you have issued
USE database before, you can leave out the
database part.

character sets
• There is a special configuration option with mysql
working on wotan that tries to ensure utf-8 is the
default character set.
[mysqld]
collation_server=utf8_unicode_ci
character_set_server=utf8
skip-character-set-client-handshake
• These options are set in a file
/etc/mysql/conf.d/local.cnf on wotan.

collations
• Collations are specifications of word order in
sorting, and equivalences in searching. They are
language specific.
• A list of collation algorithms, that are compiled
against the default unicode collection, can be
found at http://developer.mimer.com/charts/.
• If you require sorting of columns in a certain
language, look for an available collation.

INSERT
• INSERT inserts new rows into a table. In its
simples form
INSERT INTO table VALUES (value1, value2, ..);
• Example:
INSERT INTO products VALUES ('','Neufang Pils',1.23);
• Note that in the example, I insert the null string in
the first column because it is an auto_increment.
• Mark Sandford says: If you use an
auto_increment variable, you may as well have it
last.

partial INSERT
• If you are only giving a part of a record, or if you
want to enter them in a different order you will
have to give a list of column names.
INSERT INTO products (name,id) VALUES ('Neufang
Pils','');

SELECT
• This is the SQL statement to select rows from a
table. Here is the full syntax:
SELECT [options] columns [INTO file_details]
FROM table [WHERE conditions]
[GROUP BY group_type]
[HAVING where_definitions]
[ORDER BY order_type] [LIMIT limit_criteria]
[PROCEDURE proc_name(arguments)]
[lock_options]

columns to SELECT
• You can have a comma-separated list of columns
SELECT name, price FROM products;
• You can use the star to get all columns
SELECT * FROM products;

WHERE condition to SELECT
• = means equality
WHERE id = 3
• >, <, >=, <= and != also work as expected
• IS NULL tests if the value is null
• IS NOT NULL
• IN allows you to give a set
WHERE state IN ("NY","NJ","CT")

ORDER
• You can order by a field by saying ORDER BY.
• You can add ASC or DESC to achieve ascending
or descending order.
SELECT name, address FROM customers ORDER BY
name ASC

LIMIT
• This can be used to limit the amount of rows.
LIMIT 10 19
• This is useful it web sites where you show a
selection of the results.
• This ends the discussion of the SELECT
command.

UPDATE
• UPDATE [LOW_PRIORITY] [IGNORE] table SET
column1=expression1, column2=expression2...
[WHERE condition] [ORDER BY order_criteria]
[LIMIT number] ;
• This changes values in a row.
• An example is
UPDATE students SET email= 'phpguru@gmail.com'
WHERE name='Janice Insinga';
• IGNORE instructs to ignore errors.
• LOW_PRIORITY instructs to delay if the server is
busy.

DELETE
• DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
FROM table [WHERE condition] [ORDER BY
order_criteria] [LIMIT number]
• Here is a very bad example
DELETE FROM customers;
• Here is a good example
DELETE FROM customers WHERE
customer.name='Thomas Krichel‘;

PHP mySQL functions
• We are using here the new version of PHP
mySQL function, starting with mysqli_
• The interface is object-oriented, but can also be
accessed in a non-object-oriented way. This is
known as the procedural style, in the
documentation.
• You should use the online documentation at
http://php.net/mysqli

error suppression
• The function mentioned in this library usually
report any error that has occurred.
• It can be useful to suppress such errors with the
PHP error suppression operator @.
• @function() will run the function function without
reporting mistakes.
• You can then create your own customized
mistakes by checking for errors every time you
run a mysqli function. This is useful.

mysqli_connect()
• This is used to establish a connection to the
mySQL server. It is typically of the form
mysqli_connect('host', 'user', 'password');
• Example
$link= mysqli_connect('localhost','boozer','heineken');
• You can use localhost as the host name for wotan
talking to itself, but you could also connect to
other Internet hosts, if you have permission.

the mySQL connection with mysqli
• The mysqli module has the ability to handle
several connections to the mySQL server.
• Once a connection is established it is represented
by the variable returned by mysqli_connect().
• This variable, of type "resource" has the be
referenced later to let mysqli functions know what
connection you are using, because there may be
more than one open at the same time.

mysqli_connect_error()
• This function returns a string with the last
connection error.
$link = mysqli_connect("localhost", "bad_user", "");
if (!$link) {
print "Can't connect to localhost. The error is<br/>";
print mysqli_connect_error();
print "<br/>";
}
• Note the use of ! to express Boolean "not".

mysqli_error( link )
• This function return the error from the last mySQL
command. It returns false if there was no error.
$error=mysqli_error($link);
if($error) {
print "mySQL error: $error<br/>";
}
• This function requires the connection as a
parameter.
• The value returned from that function is a simple
string.
• It is a good idea to check out error messages.

mysqli_select_db()
• This command has the syntax where link is a
resource representing a connection and
database is the name of a database.
• This tells mySQL that you now want to use the
database database.
mysqli_select_db($link,'beer_shop');
• It has the same effect as issuing
USE beer_shop;
within mySQL.

mysqli_query()
• mysqli_query(link,query) send the query string
query to mySQL connection represented by link
$link = mysqli_connect("localhost", "owner", "bruch");
// you may then add some connection checks
$query="SELECT * FROM beer_shop.customers";
$result=mysqli_query($link,$query);
• Note that the query itself does not require a
terminating semicolon.
• The result is in $result.

result of mysqli_query()
• For SELECT, SHOW, DESCRIBE or EXPLAIN
mySQL queries, mysqli_query() returns a
resource that can be further examined with
mysqli_fetch_array(). This is very important
function that we look at in the next slide.
• For UPDATE, INSERT, DELETE, DROP and
others, mysqli_query() returns a Boolean value.

examining resulting rows
• mysqli_fetch_array(result) returns an array that is
the result row for the resource result representing
the most recent, or NULL if it the last result is
reached. Its results in an array that contains the
columns requested both by number and by
column name:
while($columns=mysqli_fetch_array($result)) {
print 'name: '.$columns['name'];
print 'first column: ‘.$columns[0];
}

examining a specific result
• mysqli_data_seek(result, number) sets the array
that is returned by mysqli_fetch_array to a number
number.
while($row=mysqli_fetch_array($result)) {
print 'first column: '.$row[0];
}
mysqli_data_seek($result,0);
// otherwise the second loop would not work
while($row=mysqli_fetch_array($result)) {
print 'first column: '.$row[0];
}

mysqli_num_rows()
• This command has the syntax
mysqli_num_rows(result) where the resource
result is the result of a query.
• It returns the number of rows that are in the
result.
• This is useful in announcing the number results
before display of results.

mysqli_real_escape_string()
• mysqli_real_escape_string( link,string) returns a
string escaped for the using in mySQL.
$name="John O'Guiness";
$s_name=mysqli_real_escape_string($link,$name);
print $s_name; // prints: John O'Guiness
• Note that this function makes a call to mySQL,
therefore a connection must be established before
the function can be used.
• This function guards against SQL injections.

mysqli_close(link)
• This command closes a connection. It requires
the connection as an argument, so that it knows
which connection to close.
• This is the happiest command there is, because it
means that we have finished.
• Unfortunately it is not used very often because
the mySQL connection is closed automatically
when the script finishes running.

extra: sha1()
• This is a function that calculates a combination of
40 characters from a string.
• The result of sha1() can not be translated back
into the original string.
• This makes it a good way to store password.
$s_password=sha1($password);

http://openlib.org/home/krichel
Thank you for your attention!
Please switch off machines b4 leaving!

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