Question

我正在尝试获取此查询...

    SELECT `Num_1`, COUNT(`Num_1`) AS `value_occurrence` FROM numbers WHERE MONTH(`Dates`) = 1 AND YEAR(`Dates`) = 1995 GROUP BY `Num_1` ORDER BY `value_occurrence` DESC

但对于多个列，如'Num_1'，'Num_2'，'Num_3'，'Num_4'，'Num_5'并返回每列的出现，例如'num_1_occurrence'，'num_2_occurrence'，'num_3_occurrence'， 'num_4_occurrence'，'num_5_occurrence'以及指定日期内的所有内容。

numbers table Example output

我曾尝试过使用......

    SELECT `Num_1`,`Num_2`, `Num_3`,`Num_4`,`Num_5`,COUNT(`Num_1`,`Num_2`,`Num_3`,`Num_4`,`Num_5`) AS `num_1_occurrence`,`num_2_occurrence`,`num_3_occurrence`, `num_4_occurrence`,`num_5_occurrence`FROM numbers WHERE MONTH(`Dates`) = 1 AND YEAR(`Dates`) = 1995

但只是犯了错误，我已经搜索了好几天，但没有找到正确的方法。

Answer 1

我这样做：

SELECT n.num
     , MAX(IF(n.q='n1',n.cnt,NULL)) AS num_1_occurrence
     , MAX(IF(n.q='n2',n.cnt,NULL)) AS num_2_occurrence
     , MAX(IF(n.q='n3',n.cnt,NULL)) AS num_3_occurrence
  FROM (
         SELECT 'n1'            AS q
              , n1.Num_1        AS num
              , COUNT(n1.Num_1) AS cnt
           FROM numbers n1
          WHERE n1.Dates   >= '1995-01-01'
            AND n1.Dates   <  '1995-01-01' + INTERVAL 1 MONTH
          GROUP BY n1.Num_1

          UNION ALL

         SELECT 'n2'            AS q
              , n2.Num_2        AS num
              , COUNT(n2.Num_2) AS cnt
           FROM numbers n2
          WHERE n2.Dates   >= '1995-01-01'
            AND n2.Dates   <  '1995-01-01' + INTERVAL 1 MONTH
          GROUP BY n2.Num_2

          UNION ALL

         SELECT 'n3'            AS q
              , n3.Num_3        AS num
              , COUNT(n3.Num_3) AS cnt
           FROM numbers n3
          WHERE n3.Dates   >= '1995-01-01'
            AND n3.Dates   <  '1995-01-01' + INTERVAL 1 MONTH
          GROUP BY n3.Num_3
       ) n
 GROUP BY n.num
 ORDER BY GREATEST(num_1_occurrence,num_2_occurrence,num_3_occurrence) DESC

Answer 2

我这里只做Num_1和Num_2，但我认为这是你正在寻找或关闭的。这将为您提供“高”格式的列表，其中包含原始列名称，该列中的值以及该列中该值的计数...

SELECT 'Num_1' AS field_name, Num_1 AS value, value_count
FROM (SELECT Num_1, COUNT(Num_1) AS value_count 
      FROM numbers 
      GROUP BY Num_1) AS num1_counts
WHERE MONTH(`Dates`) = 1 AND YEAR(`Dates`) = 1995

UNION 

SELECT 'Num_2' AS field_name, Num_2 AS value, value_count
FROM (SELECT Num_2, COUNT(Num_2) AS value_count 
      FROM numbers 
      GROUP BY Num_2) AS num2_counts
WHERE MONTH(`Dates`) = 1 AND YEAR(`Dates`) = 1995

按日期选择多个列，计算每列的出现次数

2 个答案: