MySQL statement to use group_concat in Update

Question

I want to copy some data from many rows to one. When I use Select everything shows as I want to but I can't convert it to Update query. Please help me to find problem The select and update are:

SELECT CONCAT( P.POST_CONTENT, GROUP_CONCAT(M.meta_value ORDER BY M.meta_id SEPARATOR 'CHAR(10)'))
FROM posts P
INNER JOIN postmeta M ON P.ID=M.post_id
WHERE M.meta_key = 'wpcf-obrazek'
GROUP BY P.ID

and

    UPDATE P, M
    SET P.post_excerpt = CONCAT( P.POST_CONTENT, GROUP_CONCAT(M.meta_value ORDER BY M.meta_id SEPARATOR 'CHAR(10)'))
    FROM posts P
    INNER JOIN postmeta M ON P.ID=M.post_id
    WHERE M.meta_key = 'wpcf-obrazek'
    GROUP BY P.ID

Error is:

#1064 - Something is wrong in your syntax obok 'FROM posts P
    INNER JOIN postmeta M ON P.ID=M.post_id
    WHERE M.meta_key ' w linii 3

Answer 1

Update should work if you join derived table with pre-processed data, please try:

UPDATE P
INNER JOIN (
             SELECT P.ID, CONCAT( P.POST_CONTENT, GROUP_CONCAT(M.meta_value ORDER BY M.meta_id SEPARATOR 'CHAR(10)')) AS data
             FROM posts P
               INNER JOIN postmeta M ON P.ID=M.post_id
             WHERE M.meta_key = 'wpcf-obrazek'
             GROUP BY P.ID
           ) AS excerpt_data ON P.ID = excerpt_data.ID
SET P.post_excerpt = excerpt_data.data;