Regarding mysql where clause with empty string

Question

My query

SELECT order_id, order_item_id, product_id, date_due, ship_via 
    FROM order_shipment 
    WHERE (product_id LIKE 'PP80403396-502%%' AND ship_via != '');

OR

SELECT order_id, order_item_id, product_id, date_due, ship_via 
    FROM order_shipment 
    WHERE (product_id LIKE 'PP80403396-502%%' AND trim(ship_via) != '');

does not give me any results.

My expectation would be to display to display the results where ship_via field is NULL or is not empty.

Answer 1

NULL is not empty string and not not empty string. And the result of comparison is neither true, nor false, it's NULL . You should use COALESCE to test for NULL or empty. Or OR .