Константин Цветков

CASE WHEN User_ID1 > User_ID2 THEN CONCAT ( User_ID2, '-', User_ID1 )
  ELSE CONCAT ( User_ID1, '-', User_ID2 )
END CASE

SELECT Concat(calendar.name, " ", calendar.year) as name, ifnull(date.value1,0) AS value
 FROM (SELECT DISTINCT date.year, month.id, month.name FROM date, month) AS calendar
   LEFT JOIN date
     ON date.year = calendar.year AND date.month_id = calendar.id
 ORDER BY calendar.year, calendar.id LIMIT 6 OFFSET 18

ограничиваясь текущим месяцем … последние 6

SELECT Concat(calendar.name, " ", calendar.year) as name, ifnull(date.value1,0) AS value
 FROM (SELECT DISTINCT date.year, month.id, month.name FROM date, month) AS calendar
   LEFT JOIN date
     ON date.year = calendar.year AND date.month_id = calendar.id
  WHERE CONCAT(calendar.year, '-', LPAD( calendar.id, 2, '0')) 
                 > LEFT(DATE_SUB(NOW(), INTERVAL 6 MONTH), 7)
 ORDER BY calendar.year, calendar.id LIMIT 6

SELECT DISTINCT tag_id FROM news_tag WHERE theme_id = КодСтрогоЗаданнойТемы

потому что он есть в обеих статьях

SELECT tag_id
  FROM news_tag
  WHERE (theme_id = 1)
  GROUP BY tag_id
  HAVING COUNT(news_id) = ( SELECT COUNT(DISTINCT(news_id)) FROM news_tag WHERE (theme_id = 1) )