sql - SQL; 只计算每列中指定的值

Question

在 SQL 中，我有一个名为“answer”的列，其值可以是 1 或 2。我需要生成一个 SQL 查询来计算每个月 1 和 2 的数量。我有以下查询，但它不起作用：

SELECT MONTH(`date`), YEAR(`date`),COUNT(`answer`=1) as yes,
COUNT(`answer`=2) as nope,` COUNT(*) as total

FROM results

GROUP BY YEAR(`date`), MONTH(`date`)

Answer 1

我会按年份、月份以及答案本身进行分组。这将导致每月两行：一个计算答案 1 的出现，另一个计算答案 2（对于其他答案值也是通用的）

SELECT MONTH(`date`), YEAR(`date`), answer, COUNT(*)
FROM results
GROUP BY YEAR(`date`), MONTH(`date`), answer

Answer 2

尝试 SUM-CASE 技巧：

SELECT 
    MONTH(`date`), 
    YEAR(`date`),
    SUM(case when `answer` = 1 then 1 else 0 end) as yes,
    SUM(case when `answer` = 2 then 1 else 0 end) as nope,
    COUNT(*) as total
FROM results
GROUP BY YEAR(`date`), MONTH(`date`)

Answer 3

SELECT year,
       month,
       answer
       COUNT(answer) AS quantity
FROM results
GROUP BY year, month, quantity

年|月|答案|数量
2001| 1| 1| 2
2001| 1| 2| 1
2004| 1| 1| 2
2004| 1| 2| 2

SELECT * FROM results;

年|月|答案
2001| 1| 1
2001| 1| 1
2001| 1| 2
2004| 1| 1
2004| 1| 1
2004| 1| 2
2004| 1| 2