最小和无限制计数

Question

我需要选择具有 3 个条件的收据：

1. 总收据 > 50 (receipt.total)
2. 相关购买不包括商品“黄瓜”(product.pname)
3. 关联产品的供应商数量（product.sid）最少

我设置了以下表格：

Receipt (bid, rdate, rtime, ptype, total)
Purchase (bid, rdate, rtime, code, units)
Product (code, pname, descr, utype, uprice, manu, sid)

样本数据：

INSERT INTO Product (code, pname, descr, utype, uprice, manu, sid) VALUES
        (987, 'Tomatoes',       'Vegetable',  'Kg',  5.99,  'manufacturer1', 111),
        (876, 'Cucumbers',      'Vegetable',  'Kg',  4.99,  'manufacturer2', 222),
        (765, 'Cornflakes',     'Cornflakes', 'Box', 15.9,  'manufacturer2', 222),
        (654, 'Camembert',      'Cheese',     'Box', 12.50, 'manufacturer2', 111),
        (543, 'sweet potato',   'Vegetable',  'Kg',  16.40, 'manufacturer3', 333),
        (432, 'red pepper',     'Vegetable',  'Kg',  15.99, 'manufacturer1', 111);
INSERT INTO Receipt (bid, rdate, rtime, ptype, total) VALUES
        (989, '18/3/2020', '10:00', 'Cash', 126.51),
        (989, '16/7/2020', '12:30', 'Credit',0),
        (989, '15/7/2020', '15:35', 'Credit',0),
        (878, '17/3/2020', '8:30',  'Cash', 60.47),
        (878, '22/7/2020', '7:00',  'Credit',0),
        (767, '13/7/2020', '22:00', 'Cash',0),
        (767, '10/3/2020', '20:30', 'Cash',42.97),
        (767, '14/5/2020', '14:25', 'Credit',0);


INSERT INTO Purchase (bid, rdate, rtime, code, units) VALUES
        (989, '18/3/2020', '10:00', 987, 5),
        (989, '18/3/2020', '10:00', 876, 3),
        (989, '18/3/2020', '10:00', 543, 4),
        (989, '18/3/2020', '10:00', 432, 1),
        (878, '17/3/2020', '8:30',  654, 1),
        (878, '17/3/2020', '8:30',  432, 3),
        (767, '10/3/2020', '20:30', 654, 2),
        (767, '10/3/2020', '20:30', 987, 3);

到目前为止，我有以下内容，但没有收到 sid 数量最少的收据：

SELECT Receipt.rdate, Receipt.rtime, Receipt.bid
FROM Receipt NATURAL JOIN Purchase NATURAL JOIN Product
WHERE total > 50 and 
NOT EXISTS(
    SELECT * FROM Product NATURAL JOIN Purchase
    WHERE Receipt.bid = Purchase.bid and Receipt.rdate = Purchase.rdate and Receipt.rtime = Purchase.rtime and Product.code = '876')
GROUP BY Receipt.rdate, Receipt.rtime, Receipt.bid
HAVING COUNT(DISTINCT Product.sid) = (SELECT MIN(mycount) 
FROM (SELECT sid,COUNT(DISTINCT Product.sid) mycount from product group by product.sid) ct);

我不允许使用 order by 和 limit。我做错了什么？

Answer 1

没有订购者：

with cte as 
 ( SELECT Receipt.rdate, Receipt.rtime, Receipt.bid,
      COUNT(DISTINCT Product.sid) as cnt, -- count per bid
      MIN(COUNT(DISTINCT Product.sid))    -- minimum count over rows
      OVER () as min_count                -- PARTITION BY needed???
   FROM Receipt NATURAL JOIN Purchase NATURAL JOIN Product
   WHERE total > 50 and 
   NOT EXISTS(
       SELECT * FROM Product NATURAL JOIN Purchase
       WHERE Receipt.bid = Purchase.bid
         and Receipt.rdate = Purchase.rdate
         and Receipt.rtime = Purchase.rtime and Product.code = '876')
   GROUP BY Receipt.rdate, Receipt.rtime, Receipt.bid
 )
select *
from cte
where cnt = min_count

简化 NOT EXISTS 逻辑：

with cte as 
 ( SELECT Receipt.rdate, Receipt.rtime, Receipt.bid,
      COUNT(DISTINCT Product.sid) as cnt, -- count per bid
      MIN(COUNT(DISTINCT Product.sid))    -- minimum count over rows
      OVER () as min_count                -- PARTITION BY needed???
   FROM Receipt NATURAL JOIN Purchase NATURAL JOIN Product
   WHERE total > 50 
   GROUP BY Receipt.rdate, Receipt.rtime, Receipt.bid
   -- will be > 0 when cucumbers exist
   HAVING count(case when product.pname = 'cucumbers' then 1 end) = 0
 )
select *
from cte
where cnt = min_count

Answer 2

这对我来说似乎是一个聚合查询：

select p.bid, p.rdate, p.rtime, sum(pr.price * p.units), count(distinct pr.sid) as num_suppliers
from purchase p join
     products pr
     on pr.code = p.code
group by p.bid, p.rdate, p.rtime
having count(*) filter (where pr.name = 'cucumbers') = 0 and
       sum(pr.price * p.units) > 50
order by count(distinct pr.sid) asc
limit 1;

我看到您的数据模型确实有 total，但没有您的数据。在这种情况下：

select p.bid, p.rdate, p.rtime, sum(pr.price * p.units), count(distinct pr.sid) as num_suppliers
from purchase p join
     products pr
     on pr.code = p.code join
     receipt r
     on r.bid = p.bid and r.rdate = p.rdate and r.rtime = p.rtime
where r.total > 50
group by p.bid, p.rdate, p.rtime
having count(*) filter (where pr.name = 'cucumbers') = 0 
order by count(distinct pr.sid) asc
limit 1;