I'm running this SQL query:
SELECT wp_woocommerce_order_items.order_id As No_Commande
FROM wp_woocommerce_order_items
LEFT JOIN
(
SELECT meta_value As Prenom
FROM wp_postmeta
WHERE meta_key = '_shipping_first_name'
) AS a
ON wp_woocommerce_order_items.order_id = a.post_id
WHERE wp_woocommerce_order_items.order_id =2198
And I get this error:
#1054 - Unknown column 'a.post_id' in 'on clause'.
I think my code is pretty simple, but I can't make it right. What am I doing wrong?
You didn't select post_id in the subquery. You have to select it in the subquery like this:
SELECT wp_woocommerce_order_items.order_id As No_Commande
FROM wp_woocommerce_order_items
LEFT JOIN
(
SELECT meta_value As Prenom, post_id -- <----- this
FROM wp_postmeta
WHERE meta_key = '_shipping_first_name'
) AS a
ON wp_woocommerce_order_items.order_id = a.post_id
WHERE wp_woocommerce_order_items.order_id =2198
I recognize that the answer works and has been accepted but there is a much cleaner way to write that query. Tested on mysql and postgres.
SELECT wpoi.order_id As No_Commande
FROM wp_woocommerce_order_items AS wpoi
LEFT JOIN wp_postmeta AS wpp ON wpoi.order_id = wpp.post_id
AND wpp.meta_key = '_shipping_first_name'
WHERE wpoi.order_id =2198
Source: Stackoverflow.com