Mysql 查询 - 按年份分组计数项目，包括“子计数”

Question

我有一个像这样的“事件”表

   id   |  user_id   |   date     |  is_important
---------------------------------------------------
   1    |     3      | 01/02/2012 |       0
   1    |     3      | 01/02/2012 |       1
   1    |     3      | 01/02/2011 |       1
   1    |     3      | 01/02/2011 |       1
   1    |     3      | 01/02/2011 |       0

基本上，我需要得到的是：

(for the user_id=3)

   year   |  count   |   count_importants
--------------------------------------------
  2012    |    2     |          1
  2011    |    3     |          2

我试过了：

SELECT YEAR(e1.date) as year,COUNT(e1.id) as count_total, aux.count_importants
FROM events e1 
LEFT JOIN 
(
  SELECT YEAR(e2.date) as year2,COUNT(e2.id) as count_importants
  FROM `events` e2
  WHERE e2.user_id=18 
  AND e2.is_important = 1
  GROUP BY year2
) AS aux ON aux.year2 = e1.year
WHERE e1.user_id=18 
GROUP BY year

但是mysql给我一个错误

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'aux ON aux.year2 = e1.year WHERE e1.user_id=18 GROUP BY year LIMIT 0, 30' at line 10

而且我已经没有办法进行这个查询 u_Uº。是否可以只使用一个查询来做到这一点？？

提前致谢

Answer 1

编辑：我认为我把事情复杂化了。你不能在一个简单的查询中做到这一点吗？

SELECT 
    YEAR(`year`) AS `year`, 
    COUNT(`id`) AS `count`, 
    SUM(`is_important`) AS `count_importants`
FROM `events`
WHERE user_id = 18
GROUP BY YEAR(`year`)

---

这是添加摘要的大解决方案 :)

考虑使用MySQL GROUP BY ROLLUP。这基本上与普通的 GROUP BY 完成类似的工作，但也会为摘要添加行。

在下面的示例中，您会看到 2000 年芬兰的两条记录，分别是 1500 英镑和 100 英镑，然后是 NULL 产品的总价值为 1600 英镑的行。它还为按分组的每个维度添加 NULL 汇总行。

来自手册：

SELECT year, country, product, SUM(profit)
FROM sales
GROUP BY year, country, product WITH ROLLUP

+------+---------+------------+-------------+
| year | country | product    | SUM(profit) |
+------+---------+------------+-------------+
| 2000 | Finland | Computer   |        1500 |
| 2000 | Finland | Phone      |         100 |
| 2000 | Finland | NULL       |        1600 |
| 2000 | India   | Calculator |         150 |
| 2000 | India   | Computer   |        1200 |
| 2000 | India   | NULL       |        1350 |
| 2000 | USA     | Calculator |          75 |
| 2000 | USA     | Computer   |        1500 |
| 2000 | USA     | NULL       |        1575 |
| 2000 | NULL    | NULL       |        4525 |
| 2001 | Finland | Phone      |          10 |
| 2001 | Finland | NULL       |          10 |
| 2001 | USA     | Calculator |          50 |
| 2001 | USA     | Computer   |        2700 |
| 2001 | USA     | TV         |         250 |
| 2001 | USA     | NULL       |        3000 |
| 2001 | NULL    | NULL       |        3010 |
| NULL | NULL    | NULL       |        7535 |
+------+---------+------------+-------------+

这是一个与您的情况特别匹配的示例：

SELECT year(`date`) AS `year`, COUNT(`id`) AS `count`, SUM(`is_important`) AS `count_importants`
FROM new_table
GROUP BY year(`date`) WITH ROLLUP;

Answer 2

别名 year - year(e1.date) AS year 在 JOIN ON 子句中不可见。尝试使用这个条件 -

...
LEFT JOIN
(
...
) ON aux.year2 = year(e1.date) -- e1.year --> year(e1.date)
...