SELECT seller_id, COUNT(*) AS item_count FROM items GROUP BY seller_id   

GROUP BY ➔ Similar to a WHERE statement but it covers all the values. The above use-case retrieves all the seller_ids and shows their item_count.

SELECT seller_id, COUNT(*) AS item_count FROM items GROUP BY seller_id HAVING item_count>2 ORDER BY item_count DESC  

HAVING ➔ HAVING is similar to WHERE, but for GROUPS.