Question

在SQL中我有一个名为“answer”的列，值可以是1或2.我需要生成一个SQL查询，它计算每个月的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，月，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的外观，另一个计算答案2（它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

尝试使用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

year|month|answer|quantity
2001|    1|     1|     2
2001|    1|     2|     1
2004|    1|     1|     2
2004|    1|     2|     2

SELECT * FROM results;

year|month|answer
2001|    1|     1
2001|    1|     1
2001|    1|     2
2004|    1|     1
2004|    1|     1
2004|    1|     2
2004|    1|     2

SQL;仅计算每列中指定的值

3 个答案: