WHERE clause great than zero still showing zero when using CASE functions

Question

I am trying the WHERE clause to filter out other data I dont want.

SELECT `post_id`,
       MAX(CASE WHEN `meta_key` = \'vlaue_1\' THEN `meta_value` ELSE NULL END         


        

Answer 1

Your WHERE logic belongs in a HAVING clause:

SELECT
    post_id,
    MAX(CASE WHEN meta_key = 'vlaue_1' THEN meta_value END) AS Customer,
    MAX(CASE WHEN meta_key = 'value_2' THEN meta_value END) AS DeliveryDate,
    MAX(CASE WHEN meta_key = 'value_3' THEN meta_value END) AS DeliveryTime,
    MAX(CASE WHEN meta_key = 'value_4' THEN meta_value END) AS DeliveryType
FROM wp_postmeta 
GROUP BY post_id
HAVING Customer > 0
ORDER BY post_id;

Note that your current WHERE clause might technically be valid MySQL:

WHERE 'Customer' > 0

However, this checks whether the string literal 'Customer' is greater than the value 0. It does not actually check the value of the customer case expression, which is not even available until after group by happens.