MYSQL按日期使用分组按多个字段计算多个字段

Question

我想通过使用第二组来计数。我有这样的数据：

id     sectionid    date

1        1          2015-09-16
2        1          2015-09-16
3        2          2015-09-16
4        2          2015-09-16
5        3          2015-09-16
6        1          2015-09-17
7        2          2015-09-18
8        2          2015-09-18

结果将是：

 Date          section1count   section2count  section3count

 2015-09-16      2               2              1
 2015-09-17      1               0              0
 2015-09-18      0               2              0

提前致谢。

Answer 1

您可以结合使用SUM()函数和GROUP BY来获取所需的结果集：

SELECT date AS Date,
       SUM(CASE WHEN sectionid=1 THEN 1 ELSE 0 END) AS section1count,
       SUM(CASE WHEN sectionid=2 THEN 1 ELSE 0 END) AS section2count,
       SUM(CASE WHEN sectionid=3 THEN 1 ELSE 0 END) AS section3count
FROM table
GROUP BY date

SQLFiddle

Answer 2

她是我的结果。您可以将其与每个部分进行比较

SELECT 
  SUM(IF( m.sectionid = 1 , 1,0)) section1count,
  SUM(IF( m.sectionid = 2 , 1,0)) section2count,
  SUM(IF( m.sectionid = 3 , 1,0)) section3count,
  m.date
   FROM myt m
   GROUP BY m.`date`;