PHP MySQL Introduction

MySQL is the most popular open-source database system.

What is MySQL?

MySQL is a database.

The data in MySQL is stored in database objects called tables.

A table is a collection of related data entries and it consists of columns and rows.

Databases are useful when storing information categorically. A company may have a database with the following tables: "Employees", "Products", "Customers" and "Orders".

Database Tables

A database most often contains one or more tables. Each table is identified by a name (e.g. "Customers" or "Orders"). Tables contain records (rows) with data.

Below is an example of a table called "Persons":

LastName	FirstName	Address	City
Hansen	Ola	Timoteivn 10	Sandnes
Svendson	Tove	Borgvn 23	Sandnes
Pettersen	Kari	Storgt 20	Stavanger

The table above contains three records (one for each person) and four columns (LastName, FirstName, Address, and City).

Queries

A query is a question or a request.

With MySQL, we can query a database for specific information and have a recordset returned.

Look at the following query:

SELECT LastName FROM Persons

The query above selects all the data in the "LastName" column from the "Persons" table, and will return a recordset like this:

LastName
Hansen
Svendson
Pettersen

Download MySQL Database

If you don't have a PHP server with a MySQL Database, you can download MySQL for free here: http://www.mysql.com/downloads/

Facts About MySQL Database

One great thing about MySQL is that it can be scaled down to support embedded database applications. Perhaps it is because of this reputation that many people believe that MySQL can only handle small to medium-sized systems.

The truth is that MySQL is the de-facto standard database for web sites that support huge volumes of both data and end users (like Friendster, Yahoo, Google).

Look at http://www.mysql.com/customers/ for an overview of companies using MySQL.

PHP MySQL Connect to a Database

The free MySQL database is very often used with PHP.

Create a Connection to a MySQL Database

Before you can access data in a database, you must create a connection to the database.

In PHP, this is done with the mysql_connect() function.

Syntax

mysql_connect(servername,username,password);

Parameter	Description
servername	Optional. Specifies the server to connect to. Default value is "localhost:3306"
username	Optional. Specifies the username to log in with. Default value is the name of the user that owns the server process
password	Optional. Specifies the password to log in with. Default is ""

Note: There are more available parameters, but the ones listed above are the most important. Visit our full PHP MySQL Reference for more details.

Example

In the following example we store the connection in a variable ($con) for later use in the script. The "die" part will be executed if the connection fails:

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

// some code

?>

Closing a Connection

The connection will be closed automatically when the script ends. To close the connection before, use the mysql_close() function:

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

// some code

mysql_close($con);

?>

PHP MySQL Create Database and Tables

A database holds one or multiple tables.

Create a Database

The CREATE DATABASE statement is used to create a database in MySQL.

Syntax

CREATE DATABASE database_name

To learn more about SQL, please visit our SQL tutorial.

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

The following example creates a database called "my_db":

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

if (mysql_query("CREATE DATABASE my_db",$con))

  {

  echo "Database created";

  }

else

  {

  echo "Error creating database: " . mysql_error();

  }

mysql_close($con);

?>

Create a Table

The CREATE TABLE statement is used to create a table in MySQL.

Syntax

CREATE TABLE table_name

(

column_name1 data_type,

column_name2 data_type,

column_name3 data_type,

....

)

To learn more about SQL, please visit our SQL tutorial.

We must add the CREATE TABLE statement to the mysql_query() function to execute the command.

Example

The following example creates a table named "Persons", with three columns. The column names will be "FirstName", "LastName" and "Age":

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

// Create database

if (mysql_query("CREATE DATABASE my_db",$con))

  {

  echo "Database created";

  }

else

  {

  echo "Error creating database: " . mysql_error();

  }

// Create table

mysql_select_db("my_db", $con);

$sql = "CREATE TABLE Persons

(

FirstName varchar(15),

LastName varchar(15),

Age int

)";

// Execute query

mysql_query($sql,$con);

mysql_close($con);

?>

Important: A database must be selected before a table can be created. The database is selected with the mysql_select_db() function.

Note: When you create a database field of type varchar, you must specify the maximum length of the field, e.g. varchar(15).

The data type specifies what type of data the column can hold. For a complete reference of all the data types available in MySQL, go to our complete Data Types reference.

Primary Keys and Auto Increment Fields

Each table should have a primary key field.

A primary key is used to uniquely identify the rows in a table. Each primary key value must be unique within the table. Furthermore, the primary key field cannot be null because the database engine requires a value to locate the record.

The following example sets the personID field as the primary key field. The primary key field is often an ID number, and is often used with the AUTO_INCREMENT setting. AUTO_INCREMENT automatically increases the value of the field by 1 each time a new record is added. To ensure that the primary key field cannot be null, we must add the NOT NULL setting to the field.

Example

$sql = "CREATE TABLE Persons

(

personID int NOT NULL AUTO_INCREMENT,

PRIMARY KEY(personID),

FirstName varchar(15),

LastName varchar(15),

Age int

)";

mysql_query($sql,$con);

PHP MySQL Insert Into

The INSERT INTO statement is used to insert new records in a table.

Insert Data Into a Database Table

The INSERT INTO statement is used to add new records to a database table.

Syntax

It is possible to write the INSERT INTO statement in two forms.

The first form doesn't specify the column names where the data will be inserted, only their values:

INSERT INTO table_name

VALUES (value1, value2, value3,...)

The second form specifies both the column names and the values to be inserted:

INSERT INTO table_name (column1, column2, column3,...)

VALUES (value1, value2, value3,...)

To learn more about SQL, please visit our SQL tutorial.

To get PHP to execute the statements above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

In the previous chapter we created a table named "Persons", with three columns; "Firstname", "Lastname" and "Age". We will use the same table in this example. The following example adds two new records to the "Persons" table:

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

mysql_select_db("my_db", $con);

mysql_query("INSERT INTO Persons (FirstName, LastName, Age)

VALUES ('Peter', 'Griffin', '35')");

mysql_query("INSERT INTO Persons (FirstName, LastName, Age)

VALUES ('Glenn', 'Quagmire', '33')");

mysql_close($con);

?>

Insert Data From a Form Into a Database

Now we will create an HTML form that can be used to add new records to the "Persons" table.

Here is the HTML form:

<html>

<body>

<form action="insert.php" method="post">

Firstname: <input type="text" name="firstname" />

Lastname: <input type="text" name="lastname" />

Age: <input type="text" name="age" />

<input type="submit" />

</form>

</body>

</html>

When a user clicks the submit button in the HTML form in the example above, the form data is sent to "insert.php".

The "insert.php" file connects to a database, and retrieves the values from the form with the PHP $_POST variables.

Then, the mysql_query() function executes the INSERT INTO statement, and a new record will be added to the "Persons" table.

Here is the "insert.php" page:

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

mysql_select_db("my_db", $con);

$sql="INSERT INTO Persons (FirstName, LastName, Age)

VALUES

('$_POST[firstname]','$_POST[lastname]','$_POST[age]')";

if (!mysql_query($sql,$con))

  {

  die('Error: ' . mysql_error());

  }

echo "1 record added";

mysql_close($con)

?>

PHP MySQL Select

The SELECT statement is used to select data from a database.

Select Data From a Database Table

The SELECT statement is used to select data from a database.

Syntax

SELECT column_name(s)

FROM table_name

To learn more about SQL, please visit our SQL tutorial.

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

The following example selects all the data stored in the "Persons" table (The * character selects all the data in the table):

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

mysql_select_db("my_db", $con);

$result = mysql_query("SELECT * FROM Persons");

while($row = mysql_fetch_array($result))

  {

  echo $row['FirstName'] . " " . $row['LastName'];

  echo "<br />";

  }

mysql_close($con);

?>

The example above stores the data returned by the mysql_query() function in the $result variable.

Next, we use the mysql_fetch_array() function to return the first row from the recordset as an array. Each call to mysql_fetch_array() returns the next row in the recordset. The while loop loops through all the records in the recordset. To print the value of each row, we use the PHP $row variable ($row['FirstName'] and $row['LastName']).

The output of the code above will be:

Peter Griffin

Glenn Quagmire

Display the Result in an HTML Table

The following example selects the same data as the example above, but will display the data in an HTML table:

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

mysql_select_db("my_db", $con);

$result = mysql_query("SELECT * FROM Persons");

echo "<table border='1'>

<tr>

<th>Firstname</th>

<th>Lastname</th>

</tr>";

while($row = mysql_fetch_array($result))

  {

  echo "<tr>";

  echo "<td>" . $row['FirstName'] . "</td>";

  echo "<td>" . $row['LastName'] . "</td>";

  echo "</tr>";

  }

echo "</table>";

mysql_close($con);

?>

The output of the code above will be:

Firstname	Lastname
Glenn	Quagmire
Peter	Griffin

PHP MySQL The Where Clause

The WHERE clause is used to filter records.

The WHERE clause

The WHERE clause is used to extract only those records that fulfill a specified criterion.

Syntax

SELECT column_name(s)

FROM table_name

WHERE column_name operator value

To learn more about SQL, please visit our SQL tutorial.

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

The following example selects all rows from the "Persons" table where "FirstName='Peter':

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

mysql_select_db("my_db", $con);

$result = mysql_query("SELECT * FROM Persons

WHERE FirstName='Peter'");

while($row = mysql_fetch_array($result))

  {

  echo $row['FirstName'] . " " . $row['LastName'];

  echo "<br />";

  }

?>

The output of the code above will be:

Peter Griffin

PHP MySQL Order By Keyword

The ORDER BY keyword is used to sort the data in a recordset.

The ORDER BY Keyword

The ORDER BY keyword is used to sort the data in a recordset.

The ORDER BY keyword sort the records in ascending order by default.

If you want to sort the records in a descending order, you can use the DESC keyword.

Syntax

SELECT column_name(s)

FROM table_name

ORDER BY column_name(s) ASC|DESC

To learn more about SQL, please visit our SQL tutorial.

Example

The following example selects all the data stored in the "Persons" table, and sorts the result by the "Age" column:

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

mysql_select_db("my_db", $con);

$result = mysql_query("SELECT * FROM Persons ORDER BY age");

while($row = mysql_fetch_array($result))

  {

  echo $row['FirstName'];

  echo " " . $row['LastName'];

  echo " " . $row['Age'];

  echo "<br />";

  }

mysql_close($con);

?>

The output of the code above will be:

Glenn Quagmire 33

Peter Griffin 35

Order by Two Columns

It is also possible to order by more than one column. When ordering by more than one column, the second column is only used if the values in the first column are equal:

SELECT column_name(s)

FROM table_name

ORDER BY column1, column2

PHP MySQL Update

The UPDATE statement is used to modify data in a table.

Update Data In a Database

The UPDATE statement is used to update existing records in a table.

Syntax

UPDATE table_name

SET column1=value, column2=value2,...

WHERE some_column=some_value

Note: Notice the WHERE clause in the UPDATE syntax. The WHERE clause specifies which record or records that should be updated. If you omit the WHERE clause, all records will be updated!

To learn more about SQL, please visit our SQL tutorial.

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

Earlier in the tutorial we created a table named "Persons". Here is how it looks:

FirstName	LastName	Age
Peter	Griffin	35
Glenn	Quagmire	33

The following example updates some data in the "Persons" table:

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

mysql_select_db("my_db", $con);

mysql_query("UPDATE Persons SET Age = '36'

WHERE FirstName = 'Peter' AND LastName = 'Griffin'");

mysql_close($con);

?>

After the update, the "Persons" table will look like this:

FirstName	LastName	Age
Peter	Griffin	36
Glenn	Quagmire	33

PHP MySQL Delete

The DELETE statement is used to delete records in a table.

Delete Data In a Database

The DELETE FROM statement is used to delete records from a database table.

Syntax

DELETE FROM table_name

WHERE some_column = some_value

Note: Notice the WHERE clause in the DELETE syntax. The WHERE clause specifies which record or records that should be deleted. If you omit the WHERE clause, all records will be deleted!

To learn more about SQL, please visit our SQL tutorial.

To get PHP to execute the statement above we must use the mysql_query() function. This function is used to send a query or command to a MySQL connection.

Example

Look at the following "Persons" table:

FirstName	LastName	Age
Peter	Griffin	35
Glenn	Quagmire	33

The following example deletes all the records in the "Persons" table where LastName='Griffin':

<?php

$con = mysql_connect("localhost","peter","abc123");

if (!$con)

  {

  die('Could not connect: ' . mysql_error());

  }

mysql_select_db("my_db", $con);

mysql_query("DELETE FROM Persons WHERE LastName='Griffin'");

mysql_close($con);

?>

After the deletion, the table will look like this:

FirstName	LastName	Age
Glenn	Quagmire	33

PHP Database ODBC

ODBC is an Application Programming Interface (API) that allows you to connect to a data source (e.g. an MS Access database).

Create an ODBC Connection

With an ODBC connection, you can connect to any database, on any computer in your network, as long as an ODBC connection is available.

Here is how to create an ODBC connection to a MS Access Database:

Open the Administrative Tools icon in your Control Panel.
Double-click on the Data Sources (ODBC) icon inside.
Choose the System DSN tab.
Click on Add in the System DSN tab.
Select the Microsoft Access Driver. Click Finish.
In the next screen, click Select to locate the database.
Give the database a Data Source Name (DSN).
Click OK.

Note that this configuration has to be done on the computer where your web site is located. If you are running Internet Information Server (IIS) on your own computer, the instructions above will work, but if your web site is located on a remote server, you have to have physical access to that server, or ask your web host to to set up a DSN for you to use.

Connecting to an ODBC

The odbc_connect() function is used to connect to an ODBC data source. The function takes four parameters: the data source name, username, password, and an optional cursor type.

The odbc_exec() function is used to execute an SQL statement.

Example

The following example creates a connection to a DSN called northwind, with no username and no password. It then creates an SQL and executes it:

$conn=odbc_connect('northwind','','');

$sql="SELECT * FROM customers";

$rs=odbc_exec($conn,$sql);

Retrieving Records

The odbc_fetch_row() function is used to return records from the result-set. This function returns true if it is able to return rows, otherwise false.

The function takes two parameters: the ODBC result identifier and an optional row number:

odbc_fetch_row($rs)

Retrieving Fields from a Record

The odbc_result() function is used to read fields from a record. This function takes two parameters: the ODBC result identifier and a field number or name.

The code line below returns the value of the first field from the record:

$compname=odbc_result($rs,1);

The code line below returns the value of a field called "CompanyName":

$compname=odbc_result($rs,"CompanyName");

Closing an ODBC Connection

The odbc_close() function is used to close an ODBC connection.

odbc_close($conn);

An ODBC Example

The following example shows how to first create a database connection, then a result-set, and then display the data in an HTML table.

<html>

<body>

<?php

$conn=odbc_connect('northwind','','');

if (!$conn)

  {exit("Connection Failed: " . $conn);}

$sql="SELECT * FROM customers";

$rs=odbc_exec($conn,$sql);

if (!$rs)

  {exit("Error in SQL");}

echo "<table><tr>";

echo "<th>Companyname</th>";

echo "<th>Contactname</th></tr>";

while (odbc_fetch_row($rs))

  {

  $compname=odbc_result($rs,"CompanyName");

  $conname=odbc_result($rs,"ContactName");

  echo "<tr><td>$compname</td>";

  echo "<td>$conname</td></tr>";

  }

odbc_close($conn);

echo "</table>";

?>

</body>

</html>