Question

我可以使用数据透视表在Excel中执行此操作，但我想找到一种直接从单个SQL查询执行此操作的方法。让我们说我有一份水果及其新鲜度清单：

**Fruit   Freshness**
Banana  New
Banana  Ripe
Apple   Ripe
Orange  Old
Cherry  New
Orange  Ripe
Apple   Old
Banana  Old
Apple   New
Apple   New
Orange  Ripe
Banana  Old
Orange  New
Cherry  New
Cherry  Ripe

我想计算＆＃34;新鲜度＆＃34;然后将事件排列为最频繁，第二频率，等等。结果看起来像这样：

**Fruit Most common 2nd most common 3rd most common**
Banana  New         Old             Ripe
Apple   Old         New             Ripe
Orange  Ripe        New             Old
Cherry  New         Ripe            NA

这可以在一个查询中使用吗？

Answer 1

您只需使用GROUP_CONCAT()汇总功能：

SELECT
  Fruit, GROUP_CONCAT(Freshness ORDER BY cnt DESC) as Common
FROM (
  SELECT Fruit, Freshness, COUNT(*) cnt
  FROM
    fruits
  GROUP BY
    Fruit, Freshness
) s

将返回如下值：

Fruit  | Common
---------------------
Banana | New,Old,Ripe
Cherry | New,Ripe
...    | ...

但是如果要将结果分成三列，则可以组合上一个查询并使用SUBSTRING_INDEX()从逗号分隔值中提取第一个，第二个和第三个值：

SELECT
  Fruit,
  SUBSTRING_INDEX(Common, ',', 1) AS most,
  CASE WHEN CommonLIKE '%,%'
       THEN SUBSTRING_INDEX(SUBSTRING_INDEX(Common, ',', 2), ',', -1) END AS second_most,
  CASE WHEN CommonLIKE '%,%,%'
       THEN SUBSTRING_INDEX(SUBSTRING_INDEX(Common, ',', 3), ',', -1) END AS third_most
FROM (
  SELECT
    Fruit, GROUP_CONCAT(Freshness ORDER BY cnt DESC) as Common
  FROM (
    SELECT Fruit, Freshness, COUNT(*) cnt
    FROM
      fruits
    GROUP BY
      Fruit, Freshness
  ) s
  GROUP BY
    Fruit
  ) s

Answer 2

SQL Server 2008及更高版本：

select fruit, [1], [2], [3] from
( select row_number() over (partition by fruit order by ct desc) as rn, fruit, freshness from (
select count(1) as ct,  fruit, freshness from f
group by fruit, freshness ) g ) src
PIVOT
(
MAX(Freshness)
FOR rn in ([1], [2], [3])
) pvt

Answer 3

试试这个

create table #fr (Fruit  varchar(20), Freshness varchar(20))
insert #fr values
('Banana' , 'New'),('Banana' , 'Ripe'),('Apple'  , 'Ripe'),('Orange' , 'Old'),('Cherry' , 'New'),
('Orange' , 'Ripe'),('Apple'  , 'Old'),('Banana' , 'Old'),('Apple'  , 'New'),('Apple'  , 'New'),
('Orange' , 'Ripe'),('Banana', 'Old'),('Orange' , 'New'),('Cherry',  'New'),('Cherry',  'Ripe')


SELECT Fruit,
       [1] Most_Common,
       [2] Second_Common,
       [3] Third_common
FROM   (SELECT Fruit,Freshness,
               Row_number()OVER(partition BY Fruit ORDER BY Count(*) DESC) rn
        FROM   #fr
        GROUP  BY Fruit,Freshness) a
       PIVOT (Max(Freshness)
             FOR rn IN([1],[2],[3])) piv

SQL查询返回最常见，第2次最常见，第3次最常见的事件

3 个答案: