计算字符串的出现次数

Question

我有一个包含3列，id，name和vote的表。他们有很多寄存器。我需要以最佳的选票余额归还寄存器。投票类型为“是”和“否”。

是 - ＆gt;加1 不 - ＆gt;减1

此列投票是一个字符串列。我正在使用SQL SERVER。

示例：

必须为我返回 Ann

Answer 1

使用条件聚合来计算卡南在答案中建议的投票数

如果你真的只想要1条记录，那么就可以这样做：

SELECT TOP 1
   name
   ,SUM(CASE WHEN vote = 'yes' THEN 1 ELSE -1 END) AS VoteTotal
FROM
   @Table
GROUP BY
   name
ORDER BY
   VoteTotal DESC

这不允许绑定，但你可以使用这种方法对响应进行排名并给你结果使用RowNum只获得1个结果或RankNum来获得关系。

;WITH cteVoteTotals AS (
    SELECT
       name
       ,SUM(CASE WHEN vote = 'yes' THEN 1 ELSE -1 END) AS VoteTotal
       ,ROW_NUMBER() OVER (PARTITION BY 1 ORDER BY SUM(CASE WHEN vote = 'yes' THEN 1 ELSE -1 END) DESC) as RowNum
       ,DENSE_RANK() OVER (PARTITION BY 1 ORDER BY SUM(CASE WHEN vote = 'yes' THEN 1 ELSE -1 END) DESC) as RankNum
    FROM
       @Table
    GROUP BY
       name
)

SELECT name, VoteTotal
FROM
    cteVoteTotals
WHERE
    RowNum = 1
    --RankNum = 1  --if you want with ties use this line instead

以下是使用的测试数据，并且将来不要只是将测试数据的图像花费2分钟来制作临时表或表变量，以便您要求帮助的人不必！ / p>

DECLARE @Table AS TABLE (id INT, name VARCHAR(25), vote VARCHAR(4))
INSERT INTO @Table (id, name, vote)
VALUES (1, 'John','no'),(2, 'John','no'),(3, 'John','yes')
,(4, 'Ann','no'),(5, 'Ann','yes'),(6, 'Ann','yes')
,(9, 'Marie','no'),(8, 'Marie','no'),(7, 'Marie','yes')
,(10, 'Matt','no'),(11, 'Matt','yes'),(12, 'Matt','yes')

Answer 2

使用此代码，

;with cte as (
select id, name, case when vote = 'yes' then 1 else -1 end as votenum from register
) select name, sum(votenum) from cte group by name

您可以根据此获得最大或最小..

Answer 3

这个给出了每个人的“是”费率：

SELECT Name, SUM(CASE WHEN Vote = 'Yes' THEN 1 ELSE 0 END)/COUNT(*) AS Rate
FROM My_Table
GROUP BY Name