Question

我正在尝试查询我的表以计算投票数，如果投票方法在列表['C', 'M', 'S', 'L', 'T', 'V', 'B', 'E']中，则将其计为1并将voting_method替换为“L”。

现在我有以下查询返回正确的结果但不处理重复项。

select `election_lbl`, `voting_method`, count(*) as numVotes 
from `gen2014` group by `election_lbl`, `voting_method` order by `election_lbl` asc 

election_lbl voting_method numVotes
2014-09-04   M                    1
2014-09-05   M                    2
2014-09-05   S                    1
2014-09-08   C                   16
2014-09-08   M                    5
2014-09-08   S                    9
2014-09-09   10                   5
2014-09-09   C                   46
2014-09-09   M                    4
2014-09-09   S                    5
2014-09-10   C                   92
2014-0g-10   M                    3
2014-09-10   S                    7
2014-09-11   C                   96
2014-09-11   M                    3
2014-09-11   S                    2
2014-09-12   C                  104
2014-09-12   M                   10
2014-09-12   S                    3
2014-09-15   C                  243
2014-09-15   M                   18
2014-09-15   S                    3
2014-09-16   10                   1
2014-09-16   C                  161
2014-09-16   M                    4
2014-09-16   S                    3
2014-09-17   C                  157
2014-09-17   M                    5
2014-09-17   S                   12

你可以看到，对于2014-09-05，我有两个vote_method M和S，这两个都在列表中。如果值在列表中，我希望理想的结果删除重复的日期字段。所以它将是2014-09-05'L'3。我不希望该日期的投票消失，所以结果应该算作一个。

将查询更改为此，但mysql说错误的语法。

select `election_lbl`, `voting_method`, count(*) as numVotes from `gen2014`
(case `voting_method` when in ('C', 'M', 'S', 'L', 'T', 'V', 'B', 'E') 
then 'L' END) group by `election_lbl`, `voting_method` order by `election_lbl` asc

表架构

CREATE TABLE `gen2014` (
 `voting_method` varchar(255) DEFAULT NULL,
 `election_lbl` date DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Answer 1

如果您只想在每个日期使用这些方法进行总投票，并列为方法＆＃39; L＆＃39;，则不要在group by中包含方法，并拥有SELECT选择'L' as voting_method

select `election_lbl`, 'L' AS `voting_method`, count(*) as numVotes 
from `gen2014` 
where voting_method IN ('C', 'M', 'S', 'L', 'T', 'V', 'B', 'E')
group by `election_lbl`
order by `election_lbl` asc

Answer 2

SELECT election_lbl
     , CASE WHEN voting_method IN ('C','M','S','L','T','V','B','E')
            THEN 'L' 
            ELSE voting_method END my_voting_method
     , COUNT(*) 
  FROM my_table 
 GROUP 
    BY my_voting_method    -- or vice
     , election_lbl;       -- versa

Answer 3

select x.`election_lbl`, x.`voting_method`, count(*) as numVotes 
from (
       select `election_lbl`, 
       CASE when `voting_method` in ('C', 'M', 'S', 'L', 'T', 'V', 'B', 'E') 
            then 'L' 
            else `voting_method` 
       END as `voting_method` 
       from `gen2014`) x
group by x.`election_lbl`, x.`voting_method` 
order by x.`election_lbl` asc

如果在列表

3 个答案: