如何提高嵌套mysql查询速度，如这个？

Question

我有一定的困难，从MySQL服务器检索快速响应而进行这样的查询：

select distinct(products.id) as product_id,products.title as product_name, (select count(id) from stock where stock.available='0' and stock.product_id=products.id) as none, 
(select count(id) from stock where stock.available='1' and stock.product_id=products.id) as available, 
(select count(id) from stock where stock.available='2' and stock.product_id=products.id) as staged, 
(select count(id) from stock where stock.available='3' and stock.product_id=products.id) as departed, 
(select count(id) from stock where stock.available='4' and stock.product_id=products.id) as delivered 
from products,stock where products.id=stock.product_id; 

我不知道是否有，将提供更快的响应任何其他查询方法。感谢名单:-)

Answer 1

事情是这样的：

SELECT 
    P.id as product_id, 
    P.title as product_name, 
    SUM(CASE WHEN S.available = 0 THEN 1 ELSE 0 END) as none, 
    SUM(CASE WHEN S.available = 1 THEN 1 ELSE 0 END) as available, 
    SUM(CASE WHEN S.available = 2 THEN 1 ELSE 0 END) as staged, 
    SUM(CASE WHEN S.available = 3 THEN 1 ELSE 0 END) as departed, 
    SUM(CASE WHEN S.available = 4 THEN 1 ELSE 0 END) as delivered 
FROM products P 
     JOIN stock S 
      ON P.id = S.product_id 
    GROUP BY P.id, 
      P.title