SKU in SQL statement

I have a custom plugin from a developer that is not available anymore and he wrote the following SQL query and now I should add the _sku to it. But I struggle to get it with all the left joins … So right now I get a result-list with product_id, post_title, date and quantity and now the resultlist should include the sku

The SQL:

SELECT PD.ID as product_id, PD.post_title, ddo.date, SUM(ddo.quantity) as quantity FROM dckk0_daily_orders ddo 
        INNER JOIN 
        ( SELECT p.ID, p.post_title FROM dckk0_posts p LEFT JOIN dckk0_postmeta pm1 ON pm1.post_id = p.ID WHERE p.post_type in('product', 'product_variation') AND p.post_status = 'publish' GROUP BY p.ID,p.post_title ) AS PD ON PD.ID = ddo.product_id 
        INNER JOIN dckk0_posts p
        ON p.ID = ddo.order_id
        WHERE p.post_status in ('wc-pending', 'wc-processing', 'wc-on-hold', 'wc-completed') AND ddo.date >= DATE_FORMAT(CURDATE(),'%Y-%m-%d')
        GROUP BY PD.post_title, ddo.date
        ORDER BY ddo.date

Thanks and any help would be awesome werner