在sql中转置数据（计算月销售数据）

Question

我的数据共有 100 行

Day         Item    Price Unit
01/01/17    jeans     15   4
01/02/17    shirt     10   3
01/01/17    skirt     20   7
01/04/17    skirt     25   1
02/01/17    jeans     5   4
02/02/17    shirt    15   3
02/01/17    skirt     24   7
03/04/17    skirt     25   5

我希望 ro 将我的数据表示为 1 月和 2 月按项目的月销售额

数据应表示为

month jeans skirt shirt total
Jan
Feb

我的代码出错了

SELECT MONTH,
MAX(CASE WHEN ITEM = 'JEANS' THEN GRANDTOTAL END) GRANDTOTAL,
MAX(CASE WHEN ITEM = 'SHIRT' THEN GRANDTOTAL END) AS GRANDTOTAL,
MAX(CASE WHEN ITEM = 'SKIRT' THEN GRANDTOTAL END) AS GRANDTOTAL, 
FROM SALES 
GROUP BY MONTH ;

我尝试了所有方法但出现错误，请帮助:)

Answer 1

每件商品的销售额定义为价格 x 单位的总和，而总销售额是所有商品的销售额之和。

查看演示： http://sqlfiddle.com/#!9/2a9e8f/1

SELECT date_format(day, '%b') as `month`,
sum(case when item='jeans' then price*unit else 0 end) as jeans,
sum(case when item='shirt' then price*unit else 0 end) as shirts,
sum(case when item='skirt' then price*unit else 0 end) as skirts,
sum(price*unit) as total
FROM myTbl
where month(day) <= 2
GROUP BY date_format(day, '%b')
ORDER BY month(day);

result:
month   jeans   shirts  skirts  total
Jan       60      30         165         255
Feb   20        45       168         233