Question

有没有办法合并这些查询，以便我得到一个明确的名称，然后是今天，明天和后天的数量

select name, SUM(qty) as qty_today, 0 as qty_tomororow, 0 as qty_om  
from order_item
where delivery_date = '2011-11-22'
group by name
union all
select name, qty as qty_today, SUM(qty) as qty_tomororow, 0 as qty_om  
from order_item
where delivery_date = '2011-11-23'
group by name
union all
select name, 0 as qty_today, 0 as qty_tomororow, SUM(qty) as qty_om  
from order_item
where delivery_date = '2011-11-24'
group by name

更新
鉴于表
name，qty，delivery_date
芝加哥，1,2011-11-22
纽约，2011年11月2日至2日芝加哥，3,2011-11-23

我希望有芝加哥，1,3,8 纽约，1,0,0

Answer 1

select name, SUM(qty) as qty_today, 0 as qty_tomororow, 0 as qty_om  
from order_item
where delivery_date IN ('2011-11-22', '2011-11-23', '2011-11-24')
group by delivery_date, name

Answer 2

如果您尝试将所有这些组合在一个数据集中，可以试试这个，

SELECT name, 
       SUM(CASE WHEN delivery_date = '2011-11-22' THEN qty 
                ELSE 0 END) AS qty_today,
       SUM(CASE WHEN delivery_date = '2011-11-23' THEN qty 
                ELSE 0 END) AS qty_tomororow,
       SUM(CASE WHEN delivery_date = '2011-11-24' THEN qty 
                ELSE 0 END) AS qty_om
from order_item
where delivery_date between '2011-11-22' and '2011-11-24'
group by name

这可以在TSQL（MS SQL）中使用，希望它与MySql中的语法相同

Answer 3

UNION / UNION ALL可以解决问题：

select name, SUM(qty) as qty_today, 0 as qty_tomororow, 0 as qty_om  
from order_item
where delivery_date = '2011-11-22'
group by name
UNION ALL
select name, qty as qty_today, SUM(qty) as qty_tomororow, 0 as qty_om  
from order_item
where delivery_date = '2011-11-23'
group by name
UNION ALL
select name, 0 as qty_today, 0 as qty_tomororow, SUM(qty) as qty_om  
from order_item
where delivery_date = '2011-11-24'
group by name

Answer 4

SELECT name, 
       SUM(if (delivery_date = '2011-11-22' , qty , 0) ) AS qty_today,
       SUM(if (delivery_date = '2011-11-23' , qty , 0) ) AS qty_tomororow,
       SUM(if (delivery_date = '2011-11-24' , qty , 0) ) AS qty_om
from order_item group by name

这是MySQL的更多风格

MySQL组合来自三个查询的数据

4 个答案: