Keys, Referential Integrity and PHP

One to Many on the Web

Music DatabaseArtist Album

Track

PK: artist_id PK: (artist_id, album_id)

FK: artist_id

PK: track_id

FK: artist_id,album_id

1 New Order2 Nick Cave3 Miles Davis

1 3 Retro1 2 Substance3 2 In a Silent Way

0 Do You Love Me 2 10 Elegia 1 1

Composite Primary Key Implications

• AUTOINCREMENT works great with single column primary key. Not so with composite keys.

• Query may require two joins (transition table)• Update, Delete may require two joins

(transition table)

Music DatabaseArtist Album

Track

PK: artist_id PK: album_id

FK: artist_id

PK: track_id

FK: artist_id,album_id

1 New Order2 Nick Cave3 Miles Davis

1 1 Retro1 2 Substance3 3 In a Silent Way

0 Do You Love Me 2 11 Elegia 1 1

Referential Integrity Review

• Referential Integrity rule: When one table has a foreign key to another table, the concept of referential integrity states that you may not add a record to the table that contains the foreign key unless there is a corresponding record in the linked table. – It also includes the techniques known as cascading

update and cascading delete, which ensure that changes made to the linked table are reflected in the primary table.

Referential Integrity and SQL

• Parent table (no foreign key)– Insert: No impact– Delete: Must prevent orphan foreign key– Modify (primary key not changed ): No impact – Modify (primary key change): Update all children

(cascade update)• Child table (foreign key)– Insert: foreign key must be valid and not null– Delete: no impact– Update: foreign key must be valid and not null

Review of PHP with One Table

• No foreign key (parent table)• Insert, Modify, Delete and Query from Web

page.

Referential Integrity and SQL

• Parent table (no foreign key)– Insert: No impact– Delete: Must prevent orphan foreign key– Modify (primary key not changed ): No impact – Modify (primary key change): Update all children

(cascade update)

PHP with Two Tables: No Foreign Key (parent table)

• Insert: No considerations• Delete: Cannot leave orphan foreign key– Prohibit deletions– Delete all children that belong to parent***– Set all children foreign key to NULL (no parent)

• Update: Cannot leave orphan foreign key– Prohibit change to primary key in parent***– Update all children with updated foreign key

Cascade Delete (Child then Parent) if(isset($_GET['deleteartist'])){$sql = 'DELETE FROM album WHERE artist_id = :artist_id';$s=$pdo->prepare($sql);$s->bindValue(':artist_id', $_POST['artist_id']);$s->execute();

$sql='DELETE FROM artist WHERE artist_id = :artist_id';$s=$pdo->prepare($sql);$s->bindValue(':artist_id', $_POST['artist_id']);$s->execute();header('Location: .');exit();}

First DELETE children

Then DELETE parent

Referential Integrity and SQL

• Child table (foreign key)– Add: foreign key must be valid and not null– Delete: no impact– Update: foreign key must be valid and not null

PHP with Two Tables: Foreign key table (child table)

• Insert: Input new data, select valid foreign key– Drop down box– Check boxes

• Delete: No considerations-just delete child• Update (no foreign key change): No

considerations-just query and update child• Update (foreign key change): select valid foreign

key – Drop down box– Check boxes

DELETE From a Child Table (index.php) No Impact

if (isset($_POST['action']) and $_POST['action'] == 'Delete'){ include $_SERVER['DOCUMENT_ROOT'] . '/connect/db.inc.php';

// Delete the joke $sql = 'DELETE FROM album WHERE album_id = :album_id'; $s = $pdo->prepare($sql); $s->bindValue(':album_id', $_POST['album_id']); $s->execute(); header('Location: .'); exit();}

INSERT into Child Table• Form to collect new data

– Create and populate Drop Down box for foreign key• Controller (index.php) 2 parts:• Part 1:

-SQL to collect foreign keys for Drop Down Box on form-load form (without values)

• Part 2:-SQL to post INSERT with form data* requires foreign key (AUTOINCREMENT handles

primary key)

SQL to collect foreign keys for Drop Down (index.php)

$result = $pdo->query('SELECT artist_id,

artist_name FROM artist');

foreach ($result as $row) { $artists[] = array(

'artist_id' => $row['artist_id'], 'artist_name' => $row['artist_name']

); }

load form (without values) index.php

include 'form.html.php';

Create and populate Drop Down box for foreign key (form.html.php)

<label for="album_name">Type the album name here:</label> <textarea id="album_name" name="album_name" rows="3" cols="40"><?php htmlout($album_name); ?></textarea>

<label for="artist">Artist:</label> <select name="artist" id="artist">

<option value="">Select one</option>

<?php foreach ($artists as $artist): ?> <option value="<?php htmlout($artist['artist_id']); ?>"><?php htmlout($artist['artist_name']);?></option>

<?php endforeach; ?> </select>

SQL to post INSERT with form data index.php

$sql = 'INSERT INTO album SET album_name = :album_name, artist_id = :artist_id';

$s = $pdo->prepare($sql); $s->bindValue(':album_name', $_POST['album_name']); //form.html.php’s album_name

$s->bindValue(':artist_id', $_POST['artist']); //form.html.php’s artist

$s->execute();

* requires foreign key (AUTOINCREMENT handles primary key)

• Form.html.php<select name="artist" id="artist">

• Index.php$s->bindValue(':artist_id', $_POST['artist']); //form.html.php’s artist

Query Child Table

include $_SERVER['DOCUMENT_ROOT'] . '/connect/db.inc.php'; // The basic SELECT statement $select = 'SELECT album_id, album_name'; $from = ' FROM album'; $where = ' WHERE TRUE'; $placeholders = array();

Allow Users to Choose Criteriaif ($_GET['artist'] != '') // Search by author { $where .= " AND artist_id = :artist_id"; $placeholders[':artist_id'] = $_GET['artist']; } if ($_GET['album_name'] != '') // search text { $where .= " AND album_name LIKE :album_name"; $placeholders[':album_name'] =

'%' . $_GET['album_name'] . '%'; } $sql = $select . $from . $where; $s = $pdo->prepare($sql); $s->execute( $placeholders);

Store Query Result for Form

foreach ($s as $row) { $albums[] = array('album_id' => $row['album_id'], 'album_name' => $row['album_name']);

} include 'albums.html.php';

Search Result Form (albums.html.php)<h1>Search Results</h1> <?php if (isset($albums)): ?> <table> <tr><th>Album Name</th><th>Options</th></tr> <?php foreach ($albums as $album): ?> <tr> <td><?php htmlout($album['album_name']); ?></td> <td> <form action="?" method="post"> <div> <input type="hidden" name="album_id" value="<?php htmlout($album['album_id']); ?>"> <input type="submit" name="action" value="Edit"> <input type="submit" name="action" value="Delete"> </div> </form> </td> </tr> <?php endforeach; ?> </table> <?php endif; ?>

UPDATE into Child Table• Query: find row to update (done)• Form: collect new data

– Create and populate Drop Down box for foreign key• Controller (index.php) 2 parts:• Part 1:

-SQL to collect foreign keys for Drop Down box on form-load form (with selected record)

• Part 2:-SQL to post UPDATE with form data* requires primary key of child and foreign key

Create and Populate Drop Down<label for="artist">Artist:</label> <select name="artist" id="artist">

<option value="">Select one</option> <?php foreach ($artists as $artist): ?>

<option value="<?php htmlout($artist['artist_id']); ?>"><?php if ($artist['artist_id'] == $artist_id) { echo ' selected'; } ?><?php htmlout($artist['artist_name']);?>

</option> <?php endforeach; ?> </select>

load form (with selected record)• Collect all data for a child to display on form (index.php)$sql = 'SELECT album_id, album_name, artist_id FROM album WHERE album_id = :album_id'; $s = $pdo->prepare($sql); $s->bindValue(':album_id', $_POST['album_id']); $s->execute();

• Where did album_id come from? albums.php.html (used for search results)

<input type="hidden" name="album_id" value="<?php htmlout($album['album_id']); ?>"> <input type="submit" name="action" value="Edit"> <input type="submit" name="action" value="Delete">

Load form (with selected record)• Store album info from query in variables (index.php)$row = $s->fetch(); $album_name = $row['album_name']; $artist_id = $row['artist_id']; $album_id = $row['album_id']; • Then load into form (form.html.php)<label for="album_name">Type the album name here:</label> <textarea id="album_name" name="album_name" rows="3" cols="40"><?php htmlout($album_name); ?></textarea> </div>

SQL to post UPDATE with form data index.php

$sql = 'UPDATE album SET album_name = :album_name, artist_id = :artist_id WHERE album_id = :album_id';

$s = $pdo->prepare($sql); $s->bindValue(':album_id', $_POST['album_id']);$s->bindValue(':album_name', $_POST['album_name']); //form.html.php’s album_name

$s->bindValue(':artist_id', $_POST['artist']); //form.html.php’s artist

$s->execute();

*requires primary key of child and foreign key

$s->bindValue(':album_id',$_POST['album_id']);//primary key

$s->bindValue(':artist_id', $_POST['artist']);//foreign key