複数の列に表示される可能性のある結果の頻度の選択（SQL）

1つのアプローチは次のとおりです：

SELECT name, COUNT(1)
  FROM (           SELECT name_1 AS name FROM mytable
         UNION ALL SELECT name_2 AS name FROM mytable
         UNION ALL SELECT name_3 AS name FROM mytable
         UNION ALL SELECT name_4 AS name FROM mytable
         UNION ALL SELECT name_5 AS name FROM mytable
       ) AS myunion
 GROUP BY name
 ORDER BY COUNT(1) DESC LIMIT 6
;

テーブルには何行ありますか？