Question

Im trying to update a value in one column based on a value in another table.

I can do this if the columns are all in the same table like this:

UPDATE wp_posts 
SET post_date = REPLACE (post_date, 'X', 'Y') 
WHERE meta_value = 'Z';

But I need to join two tables first before I can update:

SELECT * 
FROM wp_posts 
LEFT OUTER JOIN wp_postmeta ON post_id = post_id

How can I update based on the two tables I have joined?

Answer 1

Try this way, if you use SQL Server

UPDATE WP
SET WP.post_date = REPLACE(WPM.post_date, 'X', 'Y') 
FROM wp_posts WP 
   LEFT OUTER JOIN wp_postmeta WPM ON WP.post_id = WPM.post_id
WHERE WP.meta_value = 'Z';

UPDATE:

If you’re using MySQL. Here’s Update for MySQL

UPDATE wp_posts WP 
   LEFT JOIN wp_postmeta WPM ON WP.post_id = WPM.post_id
SET WP.post_date = REPLACE(WPM.post_date, 'X', 'Y') 
WHERE meta_value = 'Z';