选择Query MySql

Question

我有一个包含六列的表格如下 Home_Team | Home_Score | Away_Score | Away_Team | Home_Result | Away_Result

我想选择win，loos＆amp;的Home_Team记录输出打平。

我使用了以下查询，但是如果每个类别中的所有匹配项都显示计数，则不会计算单个总计。

select a.Home_Team,  
if(a.Home_Result = 'Win', count(a.Home_Result), 0) as Win,  
if(b.Home_Result = 'Loss', count(b.Home_Result), 0) as Loss 
from nsfa.result_main_bck as a  
join nsfa.result_main_bck as b   
on a.Home_Team = b.Home_Team  
where a.Home_Result = 'Win' and b.Home_Result = 'Loss'
Group by 1

此代码可能有什么问题

我顺便使用MySql。

此致

Answer 1

if(a.Home_Result = 'Win', count(a.Home_Result), 0) as Win,

这是一种错误的做法，而你应该使用CASE表达式以及像SUM()这样的聚合函数

sum(case when a.Home_Result = 'Win' then 1 else 0 end) as Win

Answer 2

你能不能使用这样的东西https://stackoverflow.com/a/13075582/285190不确定你为什么要加入自己的桌子

这就像

那样

select a.Home_Team,
SUM(case when a.Home_Result = 'Win' then 1 else 0 end) as Win
SUM(case when a.Home_Result = 'Loss' then 1 else 0 end) as Loss
from nsfa.result_main_bck as a
where a.Home_Result = 'Win' or a.Home_Result = 'Loss'
Group By a.Home_Team

（未经测试）