Fetch a single row from a custom table for to a given ID

Question

Fetch a single row from a custom table for to a given ID

Harman

2022年4月29日 06:51

When I want to get a single row from a custom table of my WordPress database by providing a username through a function call, it does not work. When I mention the username in the where clause of the query, however, it works. Why is that?

I am using the following code:

function gettingonly($phl) {

    global $wpdb;
    $mylink = $wpdb-get_row(
    SELECT *
    FROM $wpdb-wp_philosophy_philosopher
    WHERE philosopher=%s,
        $phl
    );
    if ($mylink) {
        print input type='text' value=' . $mylink-philosopher . '
        input type='text' value=' . $mylink-about . ';
    }
}

Is this the right method to fetch a row by providing the value through the PHP function?

Topic mysql database Wordpress

Category Web

dipali · Accepted Answer · 2015年11月30日 20:20

Try this.

function gettingonly( $phl ) {

    global $wpdb;
    $mylink = $wpdb->get_row( "SELECT * FROM wp_philosophy_philosopher WHERE philosopher="."'".$phl."'" );

    if( $mylink ){
        print "<input type='text' value='" . $mylink->philosopher . "'>
        <input type='text' value='" . $mylink->about . "'>";
    }
}

For more information read WPDB WordPress Codex Entry.

s_ha_dum · Accepted Answer · 2013年4月18日 13:59

You need to run your query through $wpdb->prepare. As is, you are sending a literal SELECT * FROM $wpdb->wp_philosophy_philosopher WHERE philosopher=%s as a query. (The $phl drops off completely.) That will trigger a MySQL error.

$mylink = $wpdb->get_row($wpdb->prepare("
    SELECT *
    FROM {$wpdb->prefix}philosophy_philosopher
    WHERE philosopher=%s",
    $phl
));

As mentioned in another answer, $wpdb->wp_philosophy_philosopher is not set, which will also trigger an error, so I altered that to be {$wpdb->prefix}philosophy_philosopher.

If you had debugging enabled you would have spotted these issues yourself. It is a good idea to enable debugging during development, and preferably on a development server.

RRikesh · Accepted Answer · 2013年4月18日 06:38

$wpdb->wp_philosophy_philosopher won't work here because it has not been defined. $wpdb->table_name works only with default tables.

You can create your own using:

$wpdb->philosophy_philosopher = $wpdb->prefix . "philosophy_philosopher";

Note that the wp_ is just the table prefix and has been omitted here because different installations can have different prefixes and that your code stop to work if you change your table prefix.

You can update your code to:

function gettingonly($phl) {

  global $wpdb;
  $wpdb->philosophy_philosopher = $wpdb->prefix . "philosophy_philosopher"; 
  $mylink = $wpdb->get_row("SELECT * FROM $wpdb->philosophy_philosopher WHERE philosopher=%s",$phl);
  #the rest of your code
}

Also, learn to prepare your statements.

Fetch a single row from a custom table for to a given ID

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