How To Exclude Results From Custom WordPress MySQL Query By Taxonomy Term

Notes:

It looks like you're not using $wpdb->prepare(), so you risk SQL injections.

I also think you're missing parentheses around the relevant OR parts, so you don't end up displaying drafts, for example.

Alternative:

Instead of writing an hardcoded SQL query, we should be able to use the WP_Query class, with some modifications through hooks/filters.

Here's an example (PHP 5.4+):

$args = [     '_meta_or_like_title' => $trimmed,        // Our new custom argument!    'post_type'           => 'product',    'post_status'         => 'publish',    'meta_query'          => [        [            'key'     => 'product_model',            'value'   => $trimmed,            // Your meta value            'compare' => 'LIKE'        ]    ],    'tax_query'    => [        [            'taxonomy'  => 'product-brand',            'field'     => 'slug',            'terms'     => $protected,        // Your terms array            'operator'  => 'NOT IN'        ]    ]];

where the custom _meta_or_like_title argument is supported by a slightly modified plugin I wrote for another question here.

Plugin:

<?php/** *  Plugin Name:   Meta OR LIKE Title query in WP_Query *  Description:   Activated through the '_meta_or_like_title' argument of WP_Query  *  Plugin URI:    http://stackoverflow.com/a/31241416/2078474 *  Plugin Author: Birgir Erlendsson (birgire) *  Version:       0.0.1 */add_action( 'pre_get_posts', function( $q ){    if( $title = $q->get( '_meta_or_like_title' ) )    {        add_filter( 'get_meta_sql', function( $sql ) use ( $title )        {            global $wpdb;            // Only run once:            static $nr = 0;             if( 0 != $nr++ ) return $sql;            // Modify WHERE part:            $sql['where'] = sprintf(                " AND ( %s OR %s ) ",                $wpdb->prepare(                     "{$wpdb->posts}.post_title LIKE '%%%s%%'",                      $wpdb->esc_like( $title )                 ),                mb_substr( $sql['where'], 5, mb_strlen( $sql['where'] ) )            );            return $sql;        });    }}, PHP_INT_MAX );