基于以下MYSQL查询，如何编写UPDATE语句以更新值？

Question

I'm using the following SQL query to get the records I need from a Wordpress database.

SELECT p.id, p.post_title, m.meta_key, m.meta_value, t.slug
FROM wp_posts p
INNER JOIN wp_postmeta m ON p.id=m.post_id 
AND m.meta_key='_subscription_sign_up_fee'
INNER JOIN wp_term_relationships AS tr ON p.id = tr.object_id
INNER JOIN wp_term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id
INNER JOIN wp_terms AS t ON tt.term_id = t.term_id    
WHERE t.slug = 'bundle'

This pulls the correct records. My issue is that I need to increase the value of the _subscription_sign_up_fee by 100.

I've tried the following

update wp_postmeta
set wp_postmeta.meta_value = wp_postmeta.meta_value + 100 
INNER JOIN wp_postmeta m ON wp_posts.id=m.post_id 
AND m.meta_key='_subscription_sign_up_fee'
INNER JOIN wp_term_relationships AS tr ON wp_posts.id = tr.object_id
INNER JOIN wp_term_taxonomy AS tt ON tr.term_taxonomy_id = tt.term_taxonomy_id
INNER JOIN wp_terms AS t ON tt.term_id = t.term_id   
WHERE t.slug = 'bundle'

and get an error saying that 'Column 'meta_value' in field list is ambiguous ' I'm pretty sure I'm not understanding the aliases. Can someone point me in the right direction?

Answer 1

The correct syntax for MySQL UPDATE JOINs is to have SET at the end. You also have some problems in that you're joining wp_postmeta twice, but lost the join with wp_posts.

Something like this should work;

UPDATE wp_postmeta m
JOIN wp_posts 
  ON wp_posts.id = m.post_id AND m.meta_key = '_subscription_sign_up_fee'
JOIN wp_term_relationships AS tr 
  ON wp_posts.id = tr.object_id
JOIN wp_term_taxonomy AS tt 
  ON tr.term_taxonomy_id = tt.term_taxonomy_id
JOIN wp_terms AS t 
  ON tt.term_id = t.term_id   
SET m.meta_value = m.meta_value + 100 
WHERE t.slug = 'bundle'

...and always remember to back up your data before running potentially destructive operations from random people on the Internet :)