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

right sorry complicated title wasn't sure how best explain.

i have following query:

select * uc_posts `postinguser` = 5 , `id` not in (select dwable uc_redwables redwabledby = 5)  union  select * uc_posts id in (select dwable uc_redwables redwabledby = 5)  order time desc limit 20 

the table uc_posts looks 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 this:

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

the output looks 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 find way substitute time in selected row(s) uc_redwables table , sort corresponding row (without updating row in uc_posts).

so 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 help? thanks!

try this:

select   p.`id` id,   p.`postinguser` postinguser,  p.`message` message,  case r.dwable   when p.id r.`time`   else p.`time`   end date_time  `uc_posts` p left join `uc_redwables` r on p.id = r.dwable p.`postinguser` = 5  , r.redwabledby = 5  order date_time desc; 

this should produce 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      *