MySQL查询返回多个总计列

Question

我的SQL表中有以下数据。

uid user category count date 
-------------------------------------------------- 
1  henry RED   4  2013-05-01 
2  john BLUE  3  2013-05-01 
3  alice RED   5  2013-05-01 
4  eric GREEN  2  2013-05-02 
5  eric BLUE  2  2013-05-02 
6  john RED   3  2013-05-02 
7  henry GREEN  2  2013-05-02 
8  eric RED   3  2013-05-03 
9  john BLUE  5  2013-05-03 

我想查询，让我回了以下数据

category 2013-05-01 2013-05-02 2013-05-03 
--------------------------------------------------- 
RED   9    3    3 
BLUE  3    2    5 
GREEN  0    4    0 

我可以用下面的查询数据的一列，但我不知道如何多列编组为如上所示。我想有一个查询，我的PHP呈现，而不是循环通过每个日期。

SELECT category, SUM(count) 
FROM dbtable 
WHERE date='2013-05-01' 
GROUP BY category; 

这可能吗？想法？

Answer 1

像这样的东西应该工作：

SELECT 
    category, 
    SUM(CASE WHEN date = '2013-05-01' THEN count END) AS `2013-05-01`, 
    SUM(CASE WHEN date = '2013-05-02' THEN count END) AS `2013-05-02`, 
    SUM(CASE WHEN date = '2013-05-03' THEN count END) AS `2013-05-03` 
FROM dbtable 
GROUP BY category