How to select from two tables where the rows may be or may not be equal and group it if they are equal I have two mysql tables of images ojm_pages_articles_photos, ojm_images_optimized but I want to select rows that are common to them and also rows that are NOT common to them. In case common rows are found, they should be grouped but in case they are not, the single rows should be selected. The problem in my code is that it only selects and group records that are found both in the two tables but i want records to also be selected when they are found only in table ojm_pages_articles_photos and not in the other one.

SELECT DISTINCT `ojm_pages_articles_photos`.`id_pages_articles_photos`, 
                `ojm_pages_articles_photos`.`url_articles_photo`, 
                `ojm_pages_articles_photos`.`id_ojm_peoples` AS `id_ojm_peoples_uploader` 
FROM    `ojm_pages_articles_photos`, 
        `ojm_images_optimized`  
WHERE `ojm_pages_articles_photos`.`url_articles_photo` LIKE '%jpeg%'
  AND `ojm_pages_articles_photos`.`url_articles_photo`=`ojm_images_optimized`.`url_image_original`
GROUP BY    `ojm_images_optimized`.`url_image_optimized`
ORDER BY    `ojm_pages_articles_photos`.`id_pages_articles_photos` DESC, 
            `ojm_images_optimized`.`optimized_is_smaller`='Oui'


I used AND  (ojm_pages_articles_photos.url_articles_photo=ojm_images_optimized.url_image_original) GROUP BY ojm_images_optimized.url_image_optimized

to select where the file is in both tables and group it but there sometimes where the files are only in table ojm_pages_articles_photos but not in the other.

How to select from those two tables where the rows may be or may not be equal and group it if they are equal ?
FULL JOIN is not implemented in MySQL. 

Possible realization (model):

SELECT filename,
       CASE SUM(table_from) WHEN 1 THEN 'In first table'
                            WHEN 2 THEN 'In second table'
                            ELSE        'In both tables'
                            END AS where_it_is
FROM ( SELECT filename, 1 AS table_from
       FROM table1
       UNION DISTINCT
       SELECT filename, 2
       FROM table2 ) AS combined_data_array
GROUP BY filename


If the field in question is unique in each separate table then use UNION ALL instead of UNION DISTINCT.