Question

I’m writing a plugin and trying to insert a new row into the wp_term_relationships table inside of a foreach loop. I know the variables have values because of a var_dump, but for some reason, I’m getting an error consistently. This shows up about 600 times on the show_errors() function:

WordPress database error: [Duplicate entry ‘0-0’ for key 1] INSERT
INTO wp_term_relationships
(object_id,term_taxonomy_id,term_order) VALUES (”,”,”)

My Code:

foreach ($cb_t2c_cat_check as $values) {
        global $wpdb;
        $prefix = $wpdb->prefix;

        $table = $prefix . 'term_relationships';
        $object_id = $values->object_id;
        $taxo_id = $values->term_taxonomy_id;
        $num_object_id = (int)$object_id;
        $num_taxo_id = (int)$taxo_id;

        //var_dump($num_object_id); //This produces values, so why are they not getting inserted into the table?
        //var_dump($num_taxo_id); //This produces values, so why are they not getting inserted into the table?

        $wpdb->insert( 
            $table, 
            array( 
                'object_id' => $num_object_id, 
                'term_taxonomy_id' => $num_taxo_id,
                'term_order' => 0
                ), '' 
            ); 

        //$wpdb->show_errors();
        //$wpdb->print_error();
        }

Answer 1

As for why it does not work: do not set third parameter of $wpdb->insert to empty string. It formats every field accordingly..

What it does now is equivalent to:

$wpdb->insert($table, array(
            'object_id' => sprintf('', $num_object_id), 
            'term_taxonomy_id' => sprintf('', $num_taxo_id),
            'term_order' => sprintf('', 0)
));

If you really want to set third parameter you should do:

$wpdb->insert($table, array(
            'object_id' => $num_object_id, 
            'term_taxonomy_id' => $num_taxo_id,
            'term_order' => 0
), array('%d', '%d', '%d'));

---

As for error: wp_term_relationships table has a unique primary key on (object_id, term_taxonomy_id). This means that you cannot have two rows in that table which have both same object_id and term_taxonomy_id.

Though this has happened because by setting third parameter of insert to empty string, you are trying to insert rows with object_id=0 and term_taxonomy_id=0 over and over again.