您需要对数据进行逆透视:

You need to unpivot the data:

SELECT tag, COUNT(*)
FROM (
    SELECT tag_1 AS tag
    UNION ALL
    SELECT tag_2 AS tag
    UNION ALL
    SELECT tag_3 AS tag
) AS X (tag)
GROUP BY tag
ORDER BY COUNT(*) DESC

我不确定如何为特定标签确定 flv，因为每个 id 可以有一个 flv 和最多 3 个标签，似乎任何标签都可以有许多不同的 flv.

I'm not sure how the flv is determined for a particular tag, since each id can have a single flv and up to 3 tags, it seems like any tag can have many different flv.