Question

我有一个包含5列的表格：

tag 1
tag 2
tag 3
tag 4
tag 5

如果我想按照这些标签的受欢迎程度（频率）显示排序结果，我会使用哪种查询？

Answer 1

由于表格未规范化，因此您必须先将其展平：

SELECT a.column, a.tag1 AS tag
  FROM TABLE a
UNION ALL
SELECT b.column, b.tag2
  FROM TABLE b
UNION ALL
SELECT c.column, c.tag3
  FROM TABLE c      
UNION ALL
SELECT d.column, d.tag4
  FROM TABLE d
UNION ALL
SELECT e.column, e.tag5
  FROM TABLE e

......在你可以数数之前：

SELECT t.tag, COUNT(*) tag_popularity
  FROM (SELECT a.column, a.tag1 AS tag
          FROM TABLE a
        UNION ALL
        SELECT b.column, b.tag2
          FROM TABLE b
        UNION ALL
        SELECT c.column, c.tag3
          FROM TABLE c      
        UNION ALL
        SELECT d.column, d.tag4
          FROM TABLE d
        UNION ALL
        SELECT e.column, e.tag5
          FROM TABLE e) x
GROUP BY x.tag
ORDER BY tag_popularity DESC

mysql - 按多个列的频率排序

1 个答案: