I have found a workaround, with three queries…
It seems that wordpress doesn’t supports SQL variables and that group_concat_max_len needs to be set in its own query.
$wpdb->query( 'SET SESSION group_concat_max_len = 1000000' );
$select_usermeta_columns_query = " SELECT
GROUP_CONCAT( DISTINCT
CONCAT(
'MAX( IF ( M.meta_key = ''',
meta_key,
''', M.meta_value, NULL)) AS `',
meta_key, '`'
)
) as select_usermeta
FROM wp_usermeta as M;";
$select_usermeta_columns = $wpdb->get_var( $select_usermeta_columns_query );
$users_info_query = " SELECT *, " . $select_usermeta_columns . "
FROM wp_users as U, wp_usermeta as M
WHERE U.id = M.user_id
GROUP BY U.id ; ";
$users_info = $wpdb->get_results( $users_info_query, OBJECT );
But I don’t like this solution because it uses 3 queries instead of 1, and I need to pass $select_usermeta_columns directly in the query ($wpdb->prepare doesn’t work for column names).
Still looking for proper solutions ??
