PHP/MySQL Have some rows in SELECT result have different values for a particular column when sorting

Question

Right sorry for the complicated title wasn't sure how to best explain.

I have the following query:

SELECT * FROM uc_posts WHERE `postinguser` = 5 AND `id` NOT IN (SELECT dwable FROM uc_redwables WHERE redwabledby = 5) 
UNION ALL 
SELECT * FROM uc_posts WHERE id IN (SELECT dwable FROM uc_redwables WHERE redwabledby = 5) 
ORDER BY time DESC LIMIT 20

The table uc_posts looks like this:

id | postinguser | time                | message |
1        5         2016-08-08 23:50:45      *
2        5         2016-08-08 23:50:35      *
3        5         2016-08-08 23:50:25      *
4        5         2016-08-08 23:50:15      *

The table uc_redwables looks like this:

id | dwable | redwabledby | time                | 
1      3          5         2016-08-08 23:51:15      

The output looks like this:

   id | postinguser | time                | message |
1        5            2016-08-08 23:50:45      *
2        5            2016-08-08 23:50:35      *
3        5            2016-08-08 23:50:25      *
4        5            2016-08-08 23:50:15      *

I'm trying to find a way to substitute the time in the selected row(s) from the uc_redwables table and sort the corresponding row with it (without actually updating that row in uc_posts ).

So that it would look like this:

   id | postinguser | time                | message |
3        5            2016-08-08 23:51:15      *     //time changed   
1        5            2016-08-08 23:50:45      *
2        5            2016-08-08 23:50:35      *
4        5            2016-08-08 23:50:15      *

Can anyone help? Thanks!

Answer 1

Try this:

SELECT 
 p.`id` as id, 
 p.`postinguser` as postinguser,
 p.`message` as message,
 case r.dwable
  when p.id then r.`time`
  else p.`time`
  end as date_time 
FROM `uc_posts` p left join `uc_redwables` r on p.id = r.dwable
WHERE p.`postinguser` = 5 
AND r.redwabledby = 5 
order by date_time desc;

This should produce an output like:

   id | postinguser | date_time                | message |
3        5            2016-08-08 23:51:15      *      
1        5            2016-08-08 23:50:45      *
2        5            2016-08-08 23:50:35      *
4        5            2016-08-08 23:50:15      *