Post on 27-Mar-2015
LIS651 lecture 2databases,
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
example: Movie database
ID | title | director | date
M1 | Gone with the wind | F. Ford Coppola | 1963
M2 | Room with a view | Coppola, F Ford | 1985
M3 | High Noon | Woody Allan | 1974
M4 | Star Wars | Steve Spielberg | 1993
M5 | Alien | Allen, Woody | 1987
M6 | Blowing in the Wind| Spielberg, Steven | 1962
• Single table• No relations between tables, of course
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 actorsID | 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
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 actorsID | sex | actor name | birth year
A1 | f | Brigitte Bardot | 1972
A2 | m | George Clooney | 1927
A3 | f | Marilyn Monroe | 1934
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 actorsID | 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 typemysql -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.
• ExampleCREATE 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 didCREATE 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 isGRANT 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 didGRANT 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 formINSERT 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 columnsSELECT name, price FROM products;
• You can use the star to get all columnsSELECT * FROM products;
WHERE condition to SELECT
• = means equalityWHERE 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 exampleDELETE FROM customers;
• Here is a good exampleDELETE 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 issuingUSE 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);
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