How to count other posts not having specific taxonomy terms?

Question

I have a custom post type "book", and a taxonomy "language" with terms "php" , "java" ,"c", "python". I want to count "book" posts not having terms "java" & "c".. such that posts with only "java" or "c" should be counted but posts with both "java" and "c" should not be counted. I tried tax_query of WP_QUERY using operator "NOT IN" and "=" but haven't got correct answer. There should be "NAND" operator for tax_query.

P.S : I have approx 20 terms and 200 posts for each. With this tax_query I have added 1 AND tax_query also and that is for other taxonomy term.

$myargs=array( 'posts_per_page' => -1, 'tax_query' => array( 'relation' => 'AND', array( 'taxonomy' => 'author', 'field' => 'slug', 'terms' => array( 'ABC', 'XYZ' ), ), array( 'taxonomy' => 'language', 'field' => 'slug', 'terms' => array( "c", "java"), 'operator' => 'NOT IN', ), ), 'post_type' => 'book');

A book may have one or more language terms.

Answer 1

There is not a NAND operator for the tax_query of WP_Query. If I understood correctly, what you intend can be rewritten this way:

1. Get all the posts without the term c.
2. Get all the posts without the term java.
3. Exclude the posts having both the terms c and java.

To achieve that, you can combine two NOT IN queries and match them with an OR:

$args = array(
    'post_type' => 'book',
    'tax_query' => array(
        'relation' => 'OR',
        array(
            'taxonomy' => 'language',
            'field'    => 'slug',
            'terms'    => array( 'c' ),
            'operator' => 'NOT IN',
        ),
        array(
            'taxonomy' => 'language',
            'field'    => 'slug',
            'terms'    => array( 'java' ),
            'operator' => 'NOT IN',
        ),
    )            
);

$posts = get_posts( $args );

echo count( $posts );

Answer 2

Hey guys somehow this helped me to get count of NAND operation. Because I dont need ti iterate through those posts, I used found_posts of WP_Query . Subtracting my posts count from total post count.

I'm still waiting for a better way if any. Thanx Luis.

$myargs=array(
'posts_per_page' => -1,
'tax_query' => array(
        'relation' => 'AND',
        array(
            'taxonomy' => 'author',
            'field'    => 'slug',
            'terms'    =>  $author_terms //array of author term slug(s),
            'operator' => 'IN'  //default operator ?

        ),
        array(
            'taxonomy' => 'language',
            'field'    => 'slug',
            'terms'    => $language_terms //array of language term slug(s)
            'operator' => 'AND' 
        )
    ),
'post_type' => 'apk');

$allargs=array(
'posts_per_page' => -1,
'tax_query' => array(
        array(
            'taxonomy' => 'author',
            'field'    => 'slug',
            'terms'    =>  $author_terms //array of author term slug(s),
            'operator' => 'IN'  //default operator ?

        )
    ),
'post_type' => 'apk');

$myquery=new WP_Query($myargs);
$allquery=new WP_Query($allargs);

echo allquery->found_posts - $myquery->found_posts;