Aren't others seeing this problem?  I can't imagine Fedora 24 is the only distro on v.5.7.11 of MySQL.  I noticed some other web apps had similar problems with this version, but their code has been updated already.  I'm wondering  if whatever the change was in MySQL, the same change wasn't made in MariaDB, and switching to that would be a workaround.  Hate to dump all my databases, remove MySQL, and install MariaDB, just to find out the same problem exists, but I'm thinking about it.

See [Github] Piwigo issue #305

I have been looking at this problem for several hours, going through on-line documentation and forums for information about the MySQL commands SELECT DISTINCT and ORDER BY.

The problem seems to be that MySQL behavior has changed with newer versions (I have 5.7.12-0ubuntu1.1 - (Ubuntu)), and that the ORDER BY columns have to be referenced in the SELECT DISTINCT part of the SQL statement.  This behavior appears to be controlled by the MySQL Server SQL Mode variable ONLY_FULL_GROUP_BY, see < http://dev.mysql.com/doc/refman/5.7/en/ … l_group_by >, < http://stackoverflow.com/questions/3469 … y-in-mysql >, < http://stackoverflow.com/questions/5391 … -statement >, and < http://dev.mysql.com/doc/refman/5.7/en/ … l_group_by > for information.

You should be able to set MySQL modes at runtime with an SQL query/command, so I had a quick look at the DB functions in Piwigo and tried to work out a way of setting the SQL mode without breaking everything else!

I seem to have had some success setting the SQL mode for the session by making a couple of additional MySQL queries to ensure ONLY_FULL_GROUP_BY is turned off for the session.  Looking through the DB abstraction layer I have made a change in ./include/dblayer/functions_mysqli.inc.php, so that after the database is opened, in function pwg_db_connect an additional query is sent to MySQL to set the server's SQL mode as desired.  It seems to be working for me! ;-)

I determined the server's SQL mode using SELECT @@SESSION.sql_mode;, then removed ONLY_FULL_GROUP_ORDER_BY from the result before sending the set command.

I placed my extra code in the  function pwg_db_connect block (near the beginning of functions_mysqli.inc.php), in an effort to limit the number of times it was used to try and reduce the database workload.

Here is a diff of my additions against the Piwigo v2.8.1 source in ./include/dblayer/functions_mysqli.inc.php,

76,90d75
<.
<   ### [START] Set Global Server variable 'ONLY_FULL_GROUP_BY' off for the session.
<   # Get current SQL Mode from server
<   ($result = $mysqli->query('SELECT @@SESSION.sql_mode;')) or my_error('SELECT @@SESSION.sql_mode;', $conf['die_on_sql_error']);
<   $sql_mode_result = $result->fetch_assoc();
<   $sql_mode = $sql_mode_result['@@SESSION.sql_mode'];
<   # Strip ONLY_FULL_GROUP_BY from result
<   $sql_mode = str_replace('ONLY_FULL_GROUP_BY,', '', $sql_mode);
<   # Ensure there is no superflous comma, in case it is reported in the middle of the string
<   $sql_mode = str_replace(',,', ',', $sql_mode);
<   # Prepend the command to set the desired runtime environment
<   $sql_mode = "SET SESSION sql_mode='".$sql_mode."';";
<   # Finally Set SQL Mode without 'ONLY_FULL_GROUP_BY'
<   ($result = $mysqli->query($sql_mode)) or my_error($sql_mode, $conf['die_on_sql_error']);
<   ### [END] Set Global Server variable 'ONLY_FULL_GROUP_BY' off for the session.
91a77
>.
148d133
<.

I hope this helps all of you that are having similar issues.

It worked in my 2.8.2! Thanks a lot. Actually, to keep things "clean", I put your hack in a separate mysql5711hack.inc.php file and included it from the functions_mysqli.inc.php file. Hopefully the Piwigo team will release an update, but at least it's working now, thanks to your help.

Regards!