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SQL in higher level languages
SQL in higher level languages
Why do we want to use SQL in a higher level
language?
1) Read in data from file, manipulate data before
insert into relation
Loop until the EOF
read values from file – higher level code
manipulate values with higher level
code
insert into relation values (SQL)
End loop
2
Why cont’d
2) Compute results based on result from query
e.g. generate a report
Query database
Compute results from query
Print results
3) Provide a user interface (Web) for SQL if the
current one is lacking
Prompt user for query
Send query to DBMS
Receive results
Display results to user
3
Must have:
to do 1) must read in values into C/C++ variables then
use those values to insert using SQL
still need SQL statement to insert, select tuples
to do 2) must be able to manipulate results from SQL
query, but mismatch between C/C++/PHP and SQL
sets versus one record at a time
to do 3) need to accept queries from user - create SQL
queries
4
To do this?
Given the query:
Select *
From department, employee
Where dno=dnumber and lname=??
What is needed?
– Variables in which to place result, select condition (Host variables)
– Processing of result table (cursors)
– Data structure for communicating with DBS in case of errors
(SQLCA)
– What if we want to process any query typed in? (Dynamic SQL)
– Also must connect to the DB, must connect to DBMS
• connect :user_name identified by :user_pwd using :host_string;
5
To do this
1.
Embedded SQL
Precede each statement with EXEC SQL
2. Platform specific classes, interfaces
Oracle’s OLE
3. Platform independent classes, interfaces
JDBC
4. Programming language that controls a software application
PHP
6
Embedded SQL
Embedded SQL – not used much these days – basis for
all others
Precede each statement with EXEC SQL
Embedded Select statement
EXEC SQL Select [distinct] expr {, expr}
into host_var {, host_var}
From table_name [alias] {, table_name [alias]}
[Where search_cond]
[Group by col {, col}]
[Having search_cond]
Embedded SQL
Only returns 1 value:
EXEC SQL select lname, salary
into :lname, :sal
From employee
Where ssn=123456789;
If Returns multiple values:
char emp_name[50][20];
int emp_number[50];
float salary[50];
EXEC SQL SELECT ENAME, EMPNO, SAL
INTO :emp_name, :emp_number, :salary FROM EMP WHERE SAL > 1000;
Embedded SQL
EXEC SQL declare c1 cursor for
Select essn, hours
From WORKS_ON
Where pno = :proj_id;
EXEC SQL open c1;
EXEC SQL fetch c1 into :essn_id, :hrs;
while (sqlca.sqlcode == 0) // checks for EOT
{
cout << essn_id << “ “ << hrs << endl;
EXEC SQL fetch c1 into :essn_id, :hrs;
};
. 2. Platform specific classes, interfaces
Oracle’s OLE
a middleware product manufactured by Oracle Corporation that
allows native access (no ODBC) to Oracle databases from client
applications via Microsoft OLE (Object Linking and Embedding)
and COM (Component Object Model)
• Native Access to Oracle and only Oracle databases
• Runs slightly faster than ODBC access
• Some people feel it is VERY convenient
OLE
• Use OLE Classes
• Example: execute SQL statements directly with the
ExecuteSQL method.
db.ExecuteSQL("insert into project values (:projectName,
:projectNumber, :projectLocation, :departmentNumber)")
OLE
Using a cursor:
ODynaset results(db, "Select * from employee");
cout << "salary" << endl;
cout << "========" << endl;
double salary;
while (!results.IsEOF()) {
if (results.GetFieldValue ("salary", &salary) == OFAILURE) {
cout << db.GetServerErrorText() << endl;
// example of character string
// char first [10];
// results.GetFieldValue("fname", first, 10);
}
else { cout << salary << endl;
results.MoveNext(); }
}
JDBC
3. Platform independent classes, interfaces
JDBC
4. PHP (and MYSQL)
PHP
• Written as a set of CGI binaries in C in 1994 by
R. Lerdorf
– Didn’t just want to post his resume
– Created PHP to display resume and collect data
about page traffic, e.g. dynamic web pages
– Personal Home Page tools publicly released 1995
– In 1998 became PHP: Hypertext Preprocessor
PHP
• Creates DYNAMIC web pages
– HTML traditionally static
– Contents regenerated every time visit or reload site
• (e.g. can include current time)
• PHP is a scripting language
– a programming language that controls a software application (program
is independent of any other application)
– Strong at communicating with program components written in other
languages
• E.g. can embed PHP statements within HTML
– Script like a dialogue for play interpreted by actors
• PHP parser with web server and web browser, model similar to MS
ASP.NET, Sun JavaServer Pages JSP
PHP
• Takes input from a file or stream containing text and PHP
instructions
• Outputs stream of data for display
• PHP originally interpreted, not converted to binary executable files
• PHP 4 – parser compiles input to produce bytecode (semi-compiled)
– Zend engine (better performance than interpreted PHP 3)
• PHP 5 – robust support for OO programming, better support for
MySQL, support for SQLite, performance enhancements
–
–
–
SQLite – ACID compliant embedded relational DB contained in small C programming
library. Source code in public domain. SQLite library is linked in and part of
application program, uses simple function calls, reducing latency. Entire DB stored
as a single file on a host machine.
PHP 6
PHP 7
PHP - specifics
•
•
•
•
•
Delimiters: <?php ?> or just <? ?>
PHP parses code within delimiters
Code outside delimiter sent to output, not parsed
Block comments /* */
Inline comments // #
PHP vs. C++
• Similarities:
– Requires semicolons after each statement ;
– Types are nearly the same (booleans, integers,
strings, etc.)
– Syntax nearly the same (For/While/If)
– Assignment is right to left ($num = 56;)
– Object-Oriented (Class support, inheritance, virtuals,
polymorphism)
– Functions!
PHP Versus C++
• Differences:
– Variables begin with $ sign ($name = “John Doe”;)
– No explicit declaration of variable types
– Introduction of “lazy” functions (foreach, explode,
mail)
– No Function Overloading
– “Hidden” functions-within-a-function
– Compiled/interpreted during every page load
– Documented!
– Echo for output
– Concatenate is dot .
PHP Versus C++
• Web Specific:
– Cookies and “Sessions”
– Dynamic HTML based on user-defined logic
– Interact and process a form’s action
– Process URL Parameters
– Easy Database Integration
Sample code
<?php // do not put a space between ? and php
Echo “Hello CS457”; // can use either “ or ‘
?>
To run this, only need to specify a link to this
program http://bama.ua.edu/~login/hello.php
Example
Easy Database Integration
• For example:
MySQL
MySQL
• MySQL is a relational DBMS
• Has many of the same capabilities as
traditional DBMSs (newest releases)
• MySQL queries mostly the same as SQL
in Oracle (subsidiary of Sun)
• Popular for web databases
• It’s freeware!
MariaDB
• open source – community maintenance
GNU GPL
• Fork of MySQL
• High compatibility with MySQL
• Developer (“Monty” Widenius) of MariaDB
is founder of MySQL –sold it to Sun
(bought by Oracle) for $1B
• Maria is his daughter
• You can connect to MySQL directly
• OR
• You can connect to MySQL through .php
Connecting directly
• You can use a tool to create tables, insert
them into your DB, query tables, etc.
• Possible tools:
– Toad: http://www.quest.com/toad-for-mysql/
– phpmyadmin
MySQL
• Or you can use a command line
• You must be able to connect to the
machine hosting the MySQL DB
MySQL
• To use a command line
• To start up MySQL type in:
mysql –u yourlogin –D yourlogin_db –p
[–h IP_address ]
It will then prompt you for your password
• You need to specify a db to use, that is the
–D parameter above
MySQL commands
Can connect directly to MySQL:
mysql> SHOW databases;
mysql> USE db_name; // must specify this each time
mysql> SHOW tables;
mysql> DESCRIBE table_name;
mysql> create table …
mysql> insert into table values (…
mysql> select * from table_name;
mysql> delete …
mysql> update
• You can connect to MySQL directly
• OR
• You can connect to MySQL through
.php, ruby on rails, etc.
Some php mysql functions
• Connecting to MySQL through PHP
– Mysql_connect (“IP_address”, “login”, “pw”)
– Mysql_select_db (‘name_db’, $link_id)
– mysql_query (string [, resource $link_id])
• Executes a query, place result in variable, like a cursor
• Resource specifies a connection, otherwise last connection opened used
• Returns a special variable holding a reference to external resource
– mysql_error ( )
• Returns error message from previous sql operation
– mysql_fetch_array ($result, how)
• Returns array corresponding to fetched row, moves pointer to next row
• Traverses through cursor of query result
• How is either mysql_assoc (use col. names) or mysql_num (use index
number) or mysql_both
– Mysql_num_fields ( $result)
• Returns number of columns in table (fields in recordset)
http://dk1.php.net/mysql_query
PHP and MySQL – ex1
<?php
$link=mysql_connect (“vrbsky-oracle.cs.ua.edu”, “login”, “pw”);
mysql_select_db('svrbsky_db') or die('Cannot select database');
$query = 'CREATE TABLE testit( '.
'id INT NOT NULL, '.
'age int)';
$result = mysql_query($query, $link);
if(!$result) {die( 'Error in SQL: ' . mysql_error());}
echo "table created";
mysql_close($link);
?>
• Example 1
Example ex2
<?php
echo "Welcome to Vrbsky's DB";
// Connect to MySQL
$link = mysql_connect(“vrbsky-oracle.cs.ua.edu", “login", “pw");
if (!$link) {die('Not connected: '. mysql_error()); } // see if connected
// Select DB will use
mysql_select_db('svrbsky') or die ('Could not select database'); // see if worked
// Now the query
$query = "Select * from testit"; // testit has 2 columns, id and age
$result = mysql_query($query, $link);
if (!$result) {die( 'Error in SQL: ' . mysql_error());}
// process results using cursor
while ($row = mysql_fetch_array($result))
{
echo "<hr>"; //horizontal line
echo "id: ". $row["id"] . "<br />";
echo "age: " . $row["age"] . "<br />";
}
mysql_free_result ($result);
mysql_close($link); // disconnecting from MySQL
?>
Try example 2
Accessing result rows
<?php
$link=mysql_connect (“vrbsky-oracle.cs.ua.edu", “login", “pw");
mysql_select_db('svrbsky') or die('Cannot select database');
$query = "SELECT id, age FROM testit";
$result = mysql_query($query, $link);
// Using an index
while($row = mysql_fetch_array($result, MYSQL_NUM))
{
echo “ID:{$row[0]} <br>" .
“Age: {$row[1]} <br><br>";
}
mysql_close($link);
?>
Example using index values
Forms and input
• Can use HTML to create forms
• Users can input values to use as host
variables in calls to mysql
HTML code
• The following code uses a form to ask for
input values to a table
• When user inputs values, event (action)
occurs and php code is executed
• To use those values in php file, must use
$_POST[‘var_name’]
$_POST function
<form method="post" action="example.php">
• variables from a form will be placed into $_POST
–
–
–
–
–
$_ POST is an associative array (key, value)
Index into array is form data name
Info sent from form
POST is a superglobal variable, available in all scopes
With POST no limits on the amount of info to send
• Different from $_GET function where
– Info sent is displayed in browser’s address bar
– Max 100 characters
HTML and PHP and MYSQL
ex3.html
<html>
<head>
</head>
<center>
<!- The following line results in php code executed after input values in form ->
<form method="post" action="example3.php">
<table>
<tr><td align="left">ID</td>
<td><input type="text" name="id"></td>
</tr>
<tr><td align="left">Age</td>
<td><input type="text" name="age" size="15"></td>
</tr>
<tr><colspan="2">
<p align="center">
<input type="submit" value="Enter record">
</td>
</tr>
</table>
</form>
</center>
</html>
PHP code
• PHP code places values input from form
into its own local variables
• Connects to database
• Inserts values into tables
• Prints out values
example3.php
<?php
// This is example3.php used in previous .htm code
$link = mysql_connect(“vrbsky-oracle.cs.ua.edu", “login", “pw");
if (!$link) {die('Not connected: '. mysql_error()); }
mysql_select_db('svrbsky') or die ('Could not select database');
//have 2 host variables
$id= $_POST['id'];
$age = $_POST['age'];
//the query
$query = "insert into testit values ('$id', '$age')";
$result = mysql_query($query);
if (!$result) {die('SQL error: ' . mysql_error());}
mysql_close($link);
print "<html><body><center>";
print "<p>You have just entered this record<p>";
print "ID: $id<br>";
print "Age: $age";
print "</body></html>";
?>
• Example 3
• example 2
• Dynamic query
Example HTML and PHP
ex4.html
<html>
<body>
<center>
<form method="post" action="example4.php">
<!-- places values in associative array called $_POST -->
<font size="18">Complete the Select Statement</font><br> Select
<input type="text" name="select" size="60" value=" " ><br>
<input type="submit" value="Get Query"></form>
<table border="1">
</table></center></body></html>
<?php //This is example4.php referenced in previous .html code
$link = mysql_connect('vrbsky-oracle.cs.ua.edu', “login", “pw");
if(!$link) { die('Not connected: '.mysql_error);}
mysql_select_db('test');
// isset tests if the value of the variable is set
if(isset($_POST['select'])) {
//$select = 'select '.$_POST['select'];
//echo $select;
//can have problems with col=.string., so must get rid of \.s inserted by php for mysql|
$select = stripslashes('select '.$_POST['select']);
echo $select;
$result = mysql_query($select, $link);
if(!$result) { echo mysql_error(); }
else {
while($row = mysql_fetch_array($result, MYSQL_NUM)) {
echo "<hr>"; // horizontal line
echo "<tr>";
for($count = 0; $count < 10; $count++) {
if(isset($row[$count])) echo " <td>{$row[$count]}</td>";
if(!isset($row[$count]) && isset($row[++$count])) {
echo "<td></td>"; $count--; }
}
echo "</tr>";
}
}
}
?>
example4.php code segment
There can be problems with col = ‘string’ so use stripslashes()
$select = stripslashes(‘select’.$_POST[‘select’]);
• http://bama.ua.edu/~svrbsky/ex4.html
Our set up
• You will use php on bama.ua.edu and
MySQL on the vrbsky-oracle machine
• The steps on the next slides tell you how
to set up your bama account
Our setup
• You need to use SSH Secure Shell to connect to
bama.ua.edu (I use ssh client from windows)
• Use vim (or whatever) to create new PHP and
HTML files
• OR you can just edit files locally then use SSH
file transfer to the bama.ua.edu machine
First Step – to set up bama
• The first step is to create your php and html files on
bama but make sure you have done the following first:
• Go to: “Change bama Shell” Web helper
– Then Put your Username and Password and check the box,
bash (Bourne Again shell)- it will enable you to do both SSH,
Telnet, FTP
– Then SSH/ Telnet to: bama.ua.edu and you can access the
public_html
– Copy or place your all your php and html files in public_html, e.g.
Hello.php
Test PHP on bama
• Create your php and html files on bama:
Create/save a .php file using an editor
• Make sure the file is on the bama.ua.edu machine in the
public_html directory
• Sample program:
<?php
Echo “Hello World”;
?>
• To run it, from a web browser, type in:
http:// bama.ua.edu/~yourbamalogin/filename
For example, I use:
http://bama.ua.edu/~svrbsky/Hello.php
html
php
1
bama.ua.edu
4
3
2
MySQL
Your DB
vrbsky-oracle
Running Examples
• Next copy some of the programs from
examples in these slides using php and
mySQL and run them.
• Make sure you change the login,
password and database to yours
• Make sure you create any needed tables
for the examples.
• Lots of great links on the web to get into
• Disadvantage: How to determine what is
error?
• FYI: phpmyadmin is a great tool if you
are interested
• Need 2 files:
– 1 for html 1 for php
• You can test your SQL statements first
using Toad (or whatever)
For the assignment - insert
tuples into your tables
• You can use a tool to insert tuples into
your tables
• Possible tools:
– Toad: http://www.quest.com/toad-for-mysql/
– Phpmyadmin
• Or Write can PHP code to:
– insert tuples into your tables/views