如何提高嵌套mysql查詢速度，如這個？

Question

我有一定的困難，從MySQL服務器檢索快速響應而進行這樣的查詢：

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，將提供更快的響應任何其他查詢方法。感謝名單:-)

Answer 1

事情是這樣的：

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