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PHP Integrating PHP with Databases Using Relational Tables Querying Multiple Tables with JOIN

Ronaldo Fialho
Ronaldo Fialho
5,105 Points

unable to retrieve single data

function full_catalog_array() { include 'connection.php';

try { $results = $db->query("SELECT media_id, title, category, img FROM Media"); } catch(Exception $e) { echo "Unable to retrieve results"; exit;
} $catalog = $results->fetchAll(); return $catalog; }

function single_item_array($id) { include 'connection.php';

try { $results = $db->query("SELECT media_id, title, category, img, format, year, genre, publisher, isbn FROM Media JOIN Genres ON Media.genre_id = Genres.genre_id LEFT OUTER JOIN Books ON Media.media_id = Books.media_id WHERE Media.media_id = $id"); } catch(Exception $e) { echo "Unable to retrieve single results"; exit;
} $catalog = $results->fetch(); return $catalog; } var_dump(single_item_array(1));

It would really help us help you if you could put this code into 3 backticks (```) so it was more readable. See the markdown Cheatsheet for more info.

1 Answer

Ronaldo, I'm going to guess that you need to specify which table some (or all, for good measure) of your SELECT fields are coming from, for example:

SELECT Media.media_id, Media.title, [...] Books.publisher, Books.isbn FROM Media [...]

Because SQL might be confused on which table you want to pull the field from.

However, you're really missing out on the built-in debugger that comes with your try-catch block, which will probably tell you exactly what's wrong and help you debug your SQL and other PHP errors for a long time to come:

try {
  // all your existing stuff
} catch(Exception $e) {
  echo "<p>Unable to retrieve single results. The error is: " . $e->getMessage() . " and the complete error object is:</p>";
  echo "<pre>";
  echo "</pre>";

The $e variable holds all the details about the error that was encountered. Its getMessage method is a great clue about what's wrong. Use it and debug easier! Hope this helps, and hope you figure it out and can get back to coding. I'd be happy to hear what you find, so come back and let me know. Good luck.

Ronaldo Fialho
Ronaldo Fialho
5,105 Points

Thx Eric!! SQLSTATE[HY000]: General error: 1 ambiguous column name: media_id

Excellent! Glad you got it. Those error messages are always so helpful for debugging.