Get products with specific attribute term and specific category term in Woocommerce using SQL

I wish to find products with two different criteria.

The code I used first to search one criteria is;

SELECT rel.object_id, rel.term_taxonomy_id, tt.taxonomy, tt.term_id, ts.name
FROM df1wrmw_term_taxonomy tt
INNER JOIN df1wrmw_term_relationships rel ON tt.term_taxonomy_id = rel.term_taxonomy_id
INNER JOIN df1wrmw_terms ts ON tt.term_id = ts.term_id
WHERE tt.taxonomy = "pa_1_scale"
AND ts.term_id = 400;

This returns all those products (Object_ID) with the attribute “pa_1_scale” and ts.term_id = 400. I can also do this to return all products with product_cat and ts.term_id = 397, using a different WHERE statement

WHERE tt.taxonomy = "product_cat"
AND ts.term_id = 397

UNION ALL just combines the two. How do I get SQL to select both these criteria? I know a WHERE statement combining the two criteria will not work as I think that no table row contains both values?

Any help available would be great.

Answer

You can try to use the following that will join duplicated tables with a different variable reference, allowing to combine both queries in one:

SELECT tr.object_id, tr.term_taxonomy_id,  tt.taxonomy,  t.term_id,  t.name,
    tr2.term_taxonomy_id as term_taxonomy_id2, tt2.taxonomy as taxonomy2, 
    t2.term_id as term_id2, t2.name as name2
FROM df1wrmw_term_relationships tr
INNER JOIN df1wrmw_term_taxonomy tt
    ON tr.term_taxonomy_id = tt.term_taxonomy_id
INNER JOIN df1wrmw_terms t
    ON tt.term_id = t.term_id
INNER JOIN df1wrmw_term_relationships tr2
    ON tr.object_id = tr2.object_id
INNER JOIN df1wrmw_term_taxonomy tt2
    ON tr2.term_taxonomy_id = tt2.term_taxonomy_id
INNER JOIN df1wrmw_terms t2
    ON tt2.term_id = t2.term_id
WHERE tt.taxonomy = 'pa_1_scale'
    AND t.term_id = 400
    AND tt2.taxonomy = 'product_cat'
    AND t2.term_id = 397

Or you can use in WordPress the class WPDB and its methods to get SQL query results in PHP:

global $wpdb;

$results = $wpdb->get_results("
    SELECT tr.object_id, tr.term_taxonomy_id,  tt.taxonomy,  t.term_id,  t.name,
        tr2.term_taxonomy_id as term_taxonomy_id2, tt2.taxonomy as taxonomy2, 
        t2.term_id as term_id2, t2.name as name2
    FROM {$wpdb->prefix}term_relationships tr
    INNER JOIN {$wpdb->prefix}term_taxonomy tt
        ON tr.term_taxonomy_id = tt.term_taxonomy_id
    INNER JOIN {$wpdb->prefix}terms t
        ON tt.term_id = t.term_id
    INNER JOIN {$wpdb->prefix}term_relationships tr2
        ON tr.object_id = tr2.object_id
    INNER JOIN {$wpdb->prefix}term_taxonomy tt2
        ON tr2.term_taxonomy_id = tt2.term_taxonomy_id
    INNER JOIN {$wpdb->prefix}terms t2
        ON tt2.term_id = t2.term_id
    WHERE tt.taxonomy = 'pa_1_scale'
        AND t.term_id = 400
        AND tt2.taxonomy = 'product_cat'
        AND t2.term_id = 397
");

// Display preformatted raw output
echo '<pre>' . print_pr($results, true) . '</pre>';

It should work.