Question

I’m trying to update a table but I need to do a left join to determine which rows I want to select.

These are two examples of what I’ve been trying, I think it’s clear what I want to do by seeing any of them:

   UPDATE `User_Likes` 
      SET `Status` = 'read'
LEFT JOIN Posts ON User_Likes.PID = Posts.ID
    WHERE Posts.UID = '1'

Here I’m trying another way:

UPDATE `User_Likes` 
   SET `Status` = 'read' 
 WHERE `ID` IN (SELECT Posts.ID
                  FROM `User_Likes`
             LEFT JOIN Posts ON User_Likes.PID = Posts.ID
                 WHERE Posts.UID = '$userID')

Answer 1

Have a look at this Example

UPDATE User_Likes
LEFT JOIN
Posts ON User_Likes.PID = Posts.ID 
SET Status='read'
WHERE Posts.UID = '1' ;

SQL Fiddle DEMO