Question

有没有办法将这两个查询结合起来？添加另一个左连接不起作用。

 select distinct 
     p.products_id,
     p.products_image,
     pd.products_name, 
     m.manufacturers_name,
     p.manufacturers_id,
     p.products_price,
     p.products_tax_class_id,
     IF(s.status, s.specials_new_products_price, NULL) as specials_new_products_price,
     IF(s.status, s.specials_new_products_price, p.products_price) as final_price
 from products_description pd,
      products p
      left join manufacturers m on p.manufacturers_id = m.manufacturers_id
      left join specials s on p.products_id = s.products_id, products_to_categories p2c
 where
          p.products_status = '1'
      and p.products_id = p2c.products_id
      and pd.products_id = p2c.products_id
      and pd.language_id = '1'
      and p2c.categories_id = '17'
 order by p.sort_order
 //-------------------
 select avg(reviews_rating) as average_rating from reviews where
 products_id = '31' and reviews_status = '1'

第一个是获取产品详细信息，第二个是获得评论表的平均评分。

Answer 1

你可以尝试一下 -

SELECT p.products_id, p.products_image, pd.products_name, m.manufacturers_name, p.manufacturers_id, p.products_price, p.products_tax_class_id, IF(s.status, s.specials_new_products_price, NULL) AS specials_new_products_price, IF(s.status, s.specials_new_products_price, p.products_price) AS final_price, AVG(rvw.reviews_rating) AS average_ratings  
FROM products p
JOIN products_to_categories p2c ON p.products_id = p2c.products_id 
JOIN products_description pd ON pd.products_id = p2c.products_id
LEFT JOIN manufacturers m ON p.manufacturers_id = m.manufacturers_id 
LEFT JOIN specials s ON p.products_id = s.products_id 
LEFT JOIN reviews rvw ON rvw.products_id=p.products_id 
WHERE p.products_status = '1' AND pd.language_id = '1' AND p2c.categories_id = '17' 
GROUP BY p.products_id 
ORDER BY p.sort_order;

注意：始终首先提及所有内部/逗号连接表，然后左键加入。

Answer 2

如何将第二个查询作为select item放在第一个查询中？

select 
    distinct p.products_id, p.products_image, pd.products_name, 
    m.manufacturers_name, p.manufacturers_id, p.products_price, p.products_tax_class_id, 
    IF(s.status, s.specials_new_products_price, NULL) as specials_new_products_price, 
    IF(s.status, s.specials_new_products_price, p.products_price) as final_price,
    (select avg(reviews_rating) as average_rating from reviews where products_id = '31' and reviews_status = '1') as average_rating
from products_description pd, products p left join manufacturers m on p.manufacturers_id = m.manufacturers_id left join specials s on p.products_id = s.products_id, products_to_categories p2c 
where p.products_status = '1' and p.products_id = p2c.products_id and pd.products_id = p2c.products_id and pd.language_id = '1' and p2c.categories_id = '17' 
order by p.sort_order

Answer 3

M在查询中没什么好处，但会尝试一下。首先，我想知道表格与评论之间是否存在关系。和＆＃39; PRODUCT_DESCRIPTION＆＃39;。如果是，那么您的组合查询可能是：

select distinct p.products_id, p.products_image, pd.products_name, m.manufacturers_name, p.manufacturers_id, p.products_price, p.products_tax_class_id,  IF(s.status, s.specials_new_products_price, NULL) as specials_new_products_price,   IF(s.status, s.specials_new_products_price, p.products_price) as final_price ,  avg(rv.reviews_rating) as average_rating   from products_description pd, reviews rv , manufacturers m, products p, specials s, products_to_categories p2c  where pd.products_id =  rv.products_id   and p.manufacturers_id = m.manufacturers_id  and p.products_id = s.products_id  and p.products_status = '1'   and p.products_id = p2c.products_id  and pd.products_id = p2c.products_id   and pd.language_id = '1'   and p2c.categories_id = '17'  and rv.products_id = '31'  and rv.reviews_status = '1'  order by p.sort_order;

MySQL avg和left join

3 个答案: