Postgresql 但它是由“罗宾汉”而不是“用户2561626”发布的。什么？！你和@RobinHood是在同一个班还是什么？这是一个正确的方式来编码这个问题吗#5@craig RingerNo，这没有任何意义。您选择的是ID号最高的产品，而不是最畅销的产品。它可能恰好适用

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但它是由“罗宾汉”而不是“用户2561626”发布的。什么？！你和@RobinHood是在同一个班还是什么？这是一个正确的方式来编码这个问题吗#5@craig RingerNo，这没有任何意义。您选择的是ID号最高的产品，而不是最畅销的产品。它可能恰好适用于示例数据，但它绝对不正确。是的！你说得对，我真是个傻瓜，没有评估，谢谢你@craig Ringer经过编辑的查询解决了问题。。无论@craig RingerNicely做了什么，它都会出错！我知道有一个简单的标准方法可以做到这一点-我完全忘记了你可以在

中按顺序引用聚合结果+1看起来不错：
--6.find most sold product with  with sales_id, product_name,quantity and sum(price)

select array_agg(s.sale_id),p.product_name,s.quantity,sum(s.price)
from products p
join sales s
on p.product_id=s.product_id;

ERROR: column "p.product_name" must appear in the GROUP BY clause or be used in an aggregate function:

SELECT 
  array_agg(s.sale_id) AS sales_ids,
  (SELECT p.product_name FROM products p WHERE p.product_id = pp.product_id) AS product_name,
  sum(s.quantity) AS total_quantity,
  sum(s.price) AS total_price
FROM
(
  -- Find the product with the largest number of sales
  -- If multiple products have the same sales an arbitrary candidate
  -- is selected; extend the ORDER BY if you want to control which
  -- one gets picked.
  SELECT 
    s2.product_id, sum(s2.quantity) AS total_quantity
  FROM sales s2
  GROUP BY s2.product_id
  ORDER BY 2 DESC
  LIMIT 1
) AS pp
INNER JOIN sales s ON (pp.product_id = s.product_id)
GROUP BY s.product_id, pp.product_id;

--1.write the query find the products which are not soled
select * 
from products 
where product_id not in (select distinct PRODUCT_ID from sales );

--9. select product details with sales_id, product_name,quantity and price those product names are started with letter ‘s’

--This selects my product details   

 select s.sale_id,p.product_name,s.quantity,s.price
    from products p,sales s
    where p.product_id=s.product_id ;

--This is'nt working to find those names which start with s.. is there any other way to solve this..
 select s.sale_id,p.product_name,s.quantity,s.price
    from products p,sales s
    where p.product_id=s.product_id and product_name = 's%';

 select array_agg(s.sale_id),p.product_name,sum(s.quantity) as Quantity ,sum(s.price) as Total_Price
    from sales s,products p
    where s.product_id =p.product_id 
    group by p.product_id  
    order by sum(s.quantity) desc limit 1  ;

select s.sale_id,p.product_name,s.quantity,s.price 
from products p,sales s
 where p.product_id=s.product_id and p.product_name LIKE 'S%';

CREATE OR REPLACE FUNCTION get_details()
  RETURNS TABLE(sale_id integer,product_name varchar,quantity integer,price int) AS
$BODY$
BEGIN
    RETURN QUERY
    select s.sale_id,p.product_name,s.quantity,s.price 
    from products p 
    join  sales s
    on p.product_id =s.product_id ;

    Exception WHEN no_data_found then
RAISE NOTICE 'No data available';
    END
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;