ottenere tutti i valori per una chiave di campo personalizzata (cross-post)

Unpossibile approcciopotrebbeessere quello di utilizzare uno deimetodi di supportonella classe WPDBpereseguire una querybasata sumetapiù raffinata. L'avvertenzaper l'utilizzo di alcune di questefunzioni,tuttavia,è che di solitonon si ottieneindietro un semplice array di datie di solito ènecessariofare riferimentiinutili alleproprietà degli oggetti,anche se si sta chiamando solo una colonna o una riga.

Ovviamente,nontutte lefunzioni sono uguali,e unamenzionemirata va almetodo WPDB ,get_col che restituisce un semplice arraypiatto del dati richiesti,faccio questamenzione specificamenteperché l'esempio seguente chiamerà questometodo.

WordPress - WPDB Selezione di una colonna di dati
$ wpdb->get_col ()

Ecco unafunzione diesempio cheinterrogail databasepertuttii post deltipo dipost scelto,lo stato delposte con unameta chiave specifica (o un campopersonalizzatoperi menoesperti ditecnologia).

 function get_meta_values( $key = '', $type = 'post', $status = 'publish' ) {

    global $wpdb;

    if( empty( $key ) )
        return;

    $r = $wpdb->get_col( $wpdb->prepare( "
        SELECT pm.meta_value FROM {$wpdb->postmeta} pm
        LEFT JOIN {$wpdb->posts} p ON p.ID = pm.post_id
        WHERE pm.meta_key = %s 
        AND p.post_status = %s 
        AND p.post_type = %s
    ", $key, $status, $type ) );

    return $r;
}
 

Quindi,adesempio,se desideri scoprire qualipost hanno unameta chiave di valutazione ,periltipo dipost film e desiderimemorizzaretaliinformazioni all'interno di una variabile,unesempio ditale chiamata sarebbe ..

 $movie_ratings = get_meta_values( 'rating', 'movies' );
 

Senon si desiderafare altro che stamparei dati sullo schermo,lafunzioneimplode di PHPpuò unire rapidamente quel semplice arrayin righe di dati.

 // Print the meta values seperate by a line break
echo implode( '<br />', get_meta_values( 'YOURKEY' ));
 

Puoi anche utilizzarei dati restituitiper calcolare quantipost hanno questimeta valorieseguendo un semplice ciclo sui dati restituitie costruendo un array dei conteggi,adesempio.

 $movie_ratings = get_meta_values( 'rating', 'movies' );
if( !empty( $movie_ratings ) ) {
    $num_of_ratings = array();
    foreach( $movie_ratings as $meta_value )
        $num_of_ratings[$meta_value] = ( isset( $num_of_ratings[$meta_value] ) ) ? $num_of_ratings[$meta_value] + 1 : 1;
}

/*
Result:
Array(
    [5] => 10
    [9] => 2
)
// ie. there are 10 movie posts with a rating of 5 and 2 movie posts with a rating of 9.
*/
 

Questa logicapotrebbeessere applicata a varitipi di datiedestesaperfunzionarein moltimodi diversi. Quindi spero chei mieiesempi siano stati utilie abbastanza semplici da seguire.

One possible approach would be to use one of the helper methods in the WPDB class to do a more refined meta based query. The caveat to using some of these functions however, is that you don't usually get back a simple array of data and usually have to make needless references to object properties, even if you're only calling for one column or row.

Of course, not all functions are the one and the same, and a purposeful mention goes out to the WPDB method, get_col which returns a simple flat array of the data queried for, i make this mention specifically because the example following will call upon this method.

WordPress - WPDB Selecting a column of data
$wpdb->get_col()

Here's an example function which queries the database for all posts of a chosen post type, post status and with a specific meta key(or custom field to the less technically minded).

function get_meta_values( $key = '', $type = 'post', $status = 'publish' ) {

    global $wpdb;

    if( empty( $key ) )
        return;

    $r = $wpdb->get_col( $wpdb->prepare( "
        SELECT pm.meta_value FROM {$wpdb->postmeta} pm
        LEFT JOIN {$wpdb->posts} p ON p.ID = pm.post_id
        WHERE pm.meta_key = %s 
        AND p.post_status = %s 
        AND p.post_type = %s
    ", $key, $status, $type ) );

    return $r;
}

So for example, if you like to find out which posts have a meta key of rating, for the post type movies and you'd like to store that information inside a variable, an example of such a call would be..

$movie_ratings = get_meta_values( 'rating', 'movies' );

If you wanted to do nothing more than print that data to screen, PHP's implode function can quickly splice that simple array into lines of data.

// Print the meta values seperate by a line break
echo implode( '<br />', get_meta_values( 'YOURKEY' ));

You can also use the returned data to work out how many posts have these meta values by doing a simple loop over the returned data and building an array of the counts, for example.

$movie_ratings = get_meta_values( 'rating', 'movies' );
if( !empty( $movie_ratings ) ) {
    $num_of_ratings = array();
    foreach( $movie_ratings as $meta_value )
        $num_of_ratings[$meta_value] = ( isset( $num_of_ratings[$meta_value] ) ) ? $num_of_ratings[$meta_value] + 1 : 1;
}

/*
Result:
Array(
    [5] => 10
    [9] => 2
)
// ie. there are 10 movie posts with a rating of 5 and 2 movie posts with a rating of 9.
*/

This logic could be applied to various kinds of data, and extended to work any number of different ways. So i hope my examples have been helpful and simple enough to follow.

Vorrei solo aggiungere unapiccola cosa al codice di t31os sopra.Ho cambiato "SELECT"in "SELECT DISTINCT"pereliminare voci duplicate quando ho usatoio stesso questo codice.

I'd just like to add one tiny thing to t31os's code above. I changed "SELECT" into "SELECT DISTINCT" to eliminate duplicate entries when I used this code myself.

Non vabene onon ènecessario utilizzareil $ wpdbglobale:

 // function to grab all possible meta values of the chosen meta key.
function get_meta_values( $meta_key,  $post_type = 'post' ) {

    $posts = get_posts(
        array(
            'post_type' => $post_type,
            'meta_key' => $meta_key,
            'posts_per_page' => -1,
        )
    );

    $meta_values = array();
    foreach( $posts as $post ) {
        $meta_values[] = get_post_meta( $post->ID, $meta_key, true );
    }

    return $meta_values;

}

$meta_values = get_meta_values( $meta_key, $post_type );
 

It is not good or needed to use the global $wpdb:

// function to grab all possible meta values of the chosen meta key.
function get_meta_values( $meta_key,  $post_type = 'post' ) {

    $posts = get_posts(
        array(
            'post_type' => $post_type,
            'meta_key' => $meta_key,
            'posts_per_page' => -1,
        )
    );

    $meta_values = array();
    foreach( $posts as $post ) {
        $meta_values[] = get_post_meta( $post->ID, $meta_key, true );
    }

    return $meta_values;

}

$meta_values = get_meta_values( $meta_key, $post_type );

ilmodopiù veloce sarebbe una query sqlpersonalizzatae nonne sono sicuro,mapuoiprovare

 $wpdb->get_results("
  SELECT posts.* , COUNT(*) 'moodcount'
  FROM $wpdb->posts as posts
  JOIN $wpdb->postmeta as postmeta
  ON postmeta.post_id = posts.ID
  AND postmeta.meta_key = 'Mood'
  GROUP BY postmeta.meta_key
");
 

Semmai è uninizio.

the fastest way would be a custom sql query and i'm not sure but you can try

$wpdb->get_results("
  SELECT posts.* , COUNT(*) 'moodcount'
  FROM $wpdb->posts as posts
  JOIN $wpdb->postmeta as postmeta
  ON postmeta.post_id = posts.ID
  AND postmeta.meta_key = 'Mood'
  GROUP BY postmeta.meta_key
");

If anything then its a start.

Per otteneretuttii meta valori da unameta chiave

Controlla wp-> db wordpress codex

 $values = $wpdb->get_col("SELECT meta_value
    FROM $wpdb->postmeta WHERE meta_key = 'yourmetakey'" );
 

For getting all meta values by a meta key

Check wp->db wordpress codex

$values = $wpdb->get_col("SELECT meta_value
    FROM $wpdb->postmeta WHERE meta_key = 'yourmetakey'" );

Non c'èmotivoper cuinon èpossibile uniret31ose il codice di Bainternetper avere un'istruzionepreparata riutilizzabile (stile wordpress) che restituiscail conteggioei valoriin un'unica operazioneefficiente.

È una querypersonalizzatama utilizza ancorail livello di astrazione del database wordpress,quindi adesempiononimporta quali siano realmentei nomi delletabelle o se cambiano,ed è un'istruzionepreparata quindi siamomoltopiù al sicuro da Attacchi SQLecc.

In questo casonon stopiù controllandoiltipo diposte stoescludendo stringhe vuote:

     $r = $wpdb->get_results(  $wpdb->prepare( "
        SELECT pm.meta_value AS name, count(*) AS count  FROM {$wpdb->postmeta} pm
        LEFT JOIN {$wpdb->posts} p ON p.ID = pm.post_id
        WHERE pm.meta_key = '%s'
        AND pm.meta_value != '' 
        AND p.post_type = '%s'
        GROUP BY pm.meta_value
        ORDER BY pm.meta_value          
        ", $key, $type) 
        );
    return $r;
 

In questoparticolare è

Questo restituirà un array di oggettiin questomodo:

 array  
 0 => 
 object(stdClass)[359]
  public 'name' => string 'Hamish' (length=6)
  public 'count' => string '3' (length=1)
 1 => 
 object(stdClass)[360]
  public 'name' => string 'Ida' (length=11)
  public 'count' => string '1' (length=1)
 2 => 
 object(stdClass)[361]
  public 'name' => string 'John' (length=12)
  public 'count' => string '1' (length=1)
 

There's no reason why you can't merge t31os and Bainternet's code to have a reusable prepared statement (wordpress style) that returns the count and the values in one efficient operation.

It's a custom query but it's still using the wordpress database abstraction layer - so for example it doesn't matter what the table names really are, or if they change, and it's a prepared statement so we're that much safer from SQL attacks etc.

In this instance I'm no longer checking for post type and I'm excluding empty strings:

    $r = $wpdb->get_results(  $wpdb->prepare( "
        SELECT pm.meta_value AS name, count(*) AS count  FROM {$wpdb->postmeta} pm
        LEFT JOIN {$wpdb->posts} p ON p.ID = pm.post_id
        WHERE pm.meta_key = '%s'
        AND pm.meta_value != '' 
        AND p.post_type = '%s'
        GROUP BY pm.meta_value
        ORDER BY pm.meta_value          
        ", $key, $type) 
        );
    return $r;

In this particular is

This will return an array of objects like so:

array  
 0 => 
 object(stdClass)[359]
  public 'name' => string 'Hamish' (length=6)
  public 'count' => string '3' (length=1)
 1 => 
 object(stdClass)[360]
  public 'name' => string 'Ida' (length=11)
  public 'count' => string '1' (length=1)
 2 => 
 object(stdClass)[361]
  public 'name' => string 'John' (length=12)
  public 'count' => string '1' (length=1)

Utilizza quanto segue conforeach

  $key = get_post_custom_values( 'key' );
 

Presume cheilnome della chiave del campopersonalizzato sia

Use the following with foreach

 $key = get_post_custom_values( 'key' );

Assumes the named of your custom field key is