Question

我的查询如下：

SELECT u.username, u.id, COUNT(t.tahmin) AS tahmins_no, 
       SUM(t.result = 1) AS winnings,
   SUM(t.result = 2) AS loses,
       (SUM(t.tahmin = 1)*1) AS ms1,
       (SUM(t.tahmin = 2)*3) AS ms0,
       (SUM(t.tahmin = 3)*1) AS ms2
FROM users u 
LEFT JOIN tahminler t ON u.id = t.user_id 

GROUP BY u.id 
HAVING tahmins_no > 0

我想使(SUM(t.tahmin = 1)*1) AS ms1仅计算result = 1（如果结果= 1添加到SUM，则不添加）结果是同一记录中的值。这可能不进行子查询吗？我不希望有复杂的未优化查询。

Answer 1

在SUM函数中使用CASE语句。

SUM( CASE When t.Result=1 Then t.tahmin Else 0 end) As ms1

Answer 2

这是你想要的吗？

SELECT u.username, u.id, COUNT(t.tahmin) AS tahmins_no, 
       SUM(t.result = 1) AS winnings,
       SUM(t.result = 2) AS loses,
       (SUM((t.tahmin = 1)*(t.result = 1))*1) AS ms1,
       (SUM((t.tahmin = 2)*(t.result = 1))*3) AS ms0,
       (SUM((t.tahmin = 3)*(t.result = 1))*1) AS ms2
FROM users u LEFT JOIN
     tahminler t
     ON u.id = t.user_id 
GROUP BY u.id 
HAVING tahmins_no > 0;

您也可以将其表达为案例陈述，例如：

sum(case when t.tahmin = 1 and t.result = 1 then 1 else 0 end) * 1 as ms1

如何在查询中进行数学运算？

2 个答案: