Question

我有以下mysql查询：

SELECT 
LEFT(MONTHNAME(date), 3) AS month,
YEAR(date) AS year,
COUNT(id) AS quantity
FROM
budgets
GROUP BY MONTH(date)

这会给我返回：

|month|year|quantity|
---------------------
|  Jan|2018|      10|
|  Mar|2018|       2|
|  May|2018|       5|

即使COUNT(id)不存在，我也需要显示月份像这样：

|month|year|quantity|
---------------------
|  Jan|2018|      10|
|  Feb|2018|       0|
|  Mar|2018|       2|
|  Apr|2018|       0|
|  May|2018|       5|

有人知道这样做吗？

更新

根据D-Shih的答案代码，查询返回以下内容：

|month|year|quantity|
---------------------
|  Jan|2018|      10|
|  Feb|null|       0|
|  Mar|2018|       2|
|  Apr|null|       0|
|  May|2018|       5|

如果我添加不同年份的寄存器，它将仅显示名称为2017的一行，如：

|month|year|quantity|
---------------------
|  Jan|2018|      10|
|  Feb|null|       0|
|  Mar|2018|       2|
|  Apr|null|       0|
|  May|2018|       5|
|  May|2017|       2|

它必须显示

|month|year|quantity|
---------------------
|  Jan|2018|      10|
|  Feb|2018|       0|
|  Mar|2018|       2|
|  Apr|2018|       0|
|  May|2018|       5|
|  Jan|2017|       0|
|  Feb|2017|       0|
|  Mar|2017|       0|
|  Apr|2017|       0|
|  May|2017|       2|

Answer 1

如果您想扩展此范围，我认为这应该可行。不确定效率如何：

SELECT a.month AS month, a.year AS year, COALESCE(b.quantity,0) AS quantity
FROM
(
   SELECT DISTINCT MONTH(date) AS month, YEAR(date) AS year
   FROM
   budgets
) a
LEFT JOIN
(
   SELECT MONTH(date) AS month, YEAR(date) AS year,
   COUNT(id) AS quantity
   FROM
   budgets
   GROUP BY MONTH(date), YEAR(date)
) b
ON a.month = b.month AND a.year = b.year

Answer 2

您可以尝试制作日历表，并根据日历表if(message.startsWith("!colorme")) { // <---- roles.some(/*..*/) //... }

OUTER JOIN

这是给您的样品。

模式（MySQL v8.0）

SELECT t1.month,
       y.year AS year,
       COUNT(t2.id) 
FROM (
    SELECT 'Jan' month
    UNION ALL
    SELECT 'Feb' month
    UNION ALL
    SELECT 'Mar' month
    UNION ALL
    SELECT 'Apr' month
    UNION ALL
    SELECT 'May' month
) t1 
CROSS JOIN (SELECT DISTINCT YEAR(date) FROM budgets) y  
LEFT JOIN budgets t2 on t1.month = LEFT(MONTHNAME(t2.date), 3) 
   AND y.year = YEAR(t2.date)
GROUP BY t1.month, y.year

查询＃1

CREATE TABLE budgets (
   `month` varchar(5),
   `year` int,
   quantity int
);


insert into budgets values ('Jan',2018,10);
insert into budgets values ('Mar',2018,2);
insert into budgets values ('May',2018,5);
insert into budgets values ('May',2017,2);

View on DB Fiddle

选择月份，年份和数量，并显示零条目的月份

2 个答案: