Someone

SELECT
          iam0.g_itemId,
          COUNT(iam1.g_itemId)
        FROM
          g2_ItemAttributesMap AS iam0,
          g2_ItemAttributesMap AS iam1,
          g2_AccessSubscriberMap, 
          g2_AccessMap
        WHERE
          iam0.g_itemId IN (267418,267297,267276,267118,267009,266976,266935,266895,266826,266757,266561,266578,266617,266671)
          AND
          iam1.g_parentSequence LIKE CONCAT(iam0.g_parentSequence, iam0.g_itemId, '/%')
          AND
          iam1.g_itemId = g2_AccessSubscriberMap.g_itemId
          AND
          g2_AccessSubscriberMap.g_accessListId = g2_AccessMap.g_accessListId
          AND
          (  g2_AccessMap.g_userId = ...
             OR
             g2_AccessMap.g_groupId IN (...)
          )
          AND 
          g2_AccessMap.g_permission = ...
        GROUP BY
          iam0.g_itemId;