Keys, Referential Integrity and PHP One to Many on the Web

Music Database ArtistAlbum Track PK: artist_id PK: (artist_id, album_id) FK: artist_id PK: track_id FK: artist_id, album_id 1New Order 2Nick Cave 3Miles Davis 13 Retro 1 2 Substance 3 2 In a Silent Way 0 Do You Love Me 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 Database ArtistAlbum Track PK: artist_id PK: album_id FK: artist_id PK: track_id FK: artist_id, album_id 1New Order 2Nick Cave 3Miles Davis 11 Retro 1 2 Substance 3 3 In a Silent Way 0 Do You Love Me 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) Type the album name here: Artist: Select one ">

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 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 Criteria if ($_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) Search Results Album Name Options <input type="hidden" name="album_id" value=" ">

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 Artist: Select one ">

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) ">

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) Type the album name here:

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